Retinoid X Receptor Is a Nonsilent Major Contributor to Vitamin D Receptor-Mediated Transcriptional Activation

Bettoun, David; Burris, Thomas P.; Houck, Keith A.; Buck, Donald W.; Stayrook, Keith R.; Khalifa, Berket; Lu, Jian-Liang; Chin, William W.; Nagpal, Sunil

doi:10.1210/me.2003-0148

Cited by 80 publications

(56 citation statements)

References 23 publications

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“…It has been demonstrated that RXR is an essential partner of VDR and actively participates in VDR-dependent gene expression [31]. Similar observations that RXR is a significant contributor to VDR-mediated gene expression have been reported elsewhere [32]. Notably, our transfection data demonstrated that retinoid alone can activate RXRα/VDR heterodimers on the ER6 response element of CYP3A4 gene.…”

Section: Discussionsupporting

confidence: 90%

Retinoids induce cytochrome P450 3A4 through RXR/VDR-mediated pathway

Wang

Chen

Xie

et al. 2008

Biochemical Pharmacology

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A panel of retinoids and carotenoids was screened as potential inducers of CYP3A4 through the RXR/VDR-mediated signaling pathway. Transient transfection assays revealed that 3 out of 12 retinoids screened transactivated RXRα/VDR and induced CYP3A4 reporter activity. These three retinoids are the active metabolites of retinoids, 9-cis-retinal, 9-cis-retinoic acid (9-cis-RA), and alltrans-retinoic acid (all-trans-RA). 9-cis-RA and all-trans-RA, preferentially transactivated the RXR/ VDR heterodimers and RXR homodimers. Retinoids and VDR agonist 1α, 25-dihydroxyvitamin D 3 , but not PXR or CAR activator, could induce Cyp3a11 mRNA level in hepatocytes derived from PXR/CAR double null mouse. Moreover, retinoids induced CYP3A4 enzyme activity in HepG2 human hepatoma and Caco-2 human colorectal adenocarcinoma cells. A direct role of retinoidmediated CYP3A4 induction through RXRα/VDR was proved by the results that 9-cis-retinal, 9-cis-RA, and all-trans-RA recruited RXRα and VDR to CYP3A4 regulatory region pER6 (proximal everted repeat with a 6-nucleotide spacer) and dXREM (distal xenobiotic-responsive enhancer module). Thus, using various approaches, we have unequivocally demonstrated that retinoids transactivate RXR/VDR heterodimers and RXR homodimers and induce CYP3A expression at mRNA as well as enzyme activity levels in both liver and intestinal cells. It is possible that retinoids might alter endobiotic metabolism through CYP3A4 induction in vivo.

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Section: Discussionsupporting

confidence: 90%

Retinoids induce cytochrome P450 3A4 through RXR/VDR-mediated pathway

Wang

Chen

Xie

et al. 2008

Biochemical Pharmacology

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“…In contrast, we found that the baseline GFP-VDR distribution in ROS17/2.8 (A1G) cells was predominantly cytoplasmic (>70%), a finding that confirms what others have reported for VDR distribution in ROS 17/2.8 cells [Racz and Barsony, 1999], COS-1 (Sunn et al, 2001), and COS-7 [Racz andBarsony, 1999] kidney cells, and microwave-fixed fibroblasts [Barsony et al, 1990]. Next, [Fleet, 2004], including Caco-2 cells [Wali et al, 1992;Tien et al, 1993;Bettoun et al, 2003]. However, our inability to see membrane-associated GFP-VDR could reflect several factors including low sensitivity of the method to detect the 1-3% of VDR that is proposed to be associated with the membrane or an inability of the GFP-VDR to associate with the membrane.…”

supporting

confidence: 89%

“…Our observation is consistent with what Barsony et al [1997] reported using a BODIPY-labeled 1,25(OH) 2 D 3 in human fibro-blasts. This does not support a role for a membrane-associated VDR as the mediator responsible for the activation of various kinases and signal transduction pathways by 1,25(OH) 2 D 3 that have been observed in a variety of cell types [Fleet, 2004], including Caco-2 cells [Wali et al, 1992;Tien et al, 1993;Bettoun et al, 2003]. However, our inability to see membrane-associated GFP-VDR could reflect several factors including low sensitivity of the method to detect the 1-3% of VDR that is proposed to be associated with the membrane or an inability of the GFP-VDR to associate with the membrane.…”

Section: Discussionmentioning

confidence: 72%

Nucleo‐cytoplasmic cycling of the vitamin D receptor in the enterocyte‐like cell line, Caco‐2

Kłopot

Hance

Peleg

et al. 2006

J of Cellular Biochemistry

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We examined the effects of 1,25 dihydroxyvitamin D 3 (1,25(OH) 2 D 3 ) on the distribution and mobility of the vitamin D receptor (VDR) in the enterocyte-like Caco-2 cell. Confocal microscopy showed that a green fluorescent protein-vitamin D receptor (GFP-VDR) fusion protein is predominantly nuclear (58%) and it does not associate with the apical or basolateral membrane of proliferating or polarized, differentiated cells. In contrast to the previously studied cell types, neither endogenous VDR nor GFP-VDR levels accumulate in the nucleus following 1,25(OH) 2 D 3 treatment (100 nM, 30 min). However, in nuclear photobleaching experiments nuclear GFP-VDR import was significantly increased by 1,25(OH) 2 D 3 during both an early (0-5 min) and later (30-35 min) period (20% per 5 min). Compared to the natural ligand, nuclear import of GFP-VDR was 60% lower in cells treated with the 1,25(OH) 2 D 3 analog, 1-alpha-fluoro-16-ene-20-epi-23-ene-26,27-bishomo-25-hydroxyvitamin D 3 (Ro-26-9228, 5 min, 100 nM). Downstream events like ligandinduced association of VDR with chromatin at 1 h and the accumulation of CYP24 mRNA were significantly lower in Ro-26-9228 treated cells compared to 1,25(OH) 2 D 3 (60 and 95% lower, respectively). Collectively our data are consistent with a role for ligand-induced nuclear VDR import in receptor activation. In addition, ligand-dependent VDR nuclear import appears to be balanced by export, thus accounting for the lack of nuclear VDR accumulation even when VDR import is significantly elevated. Keywords intestine; nuclear trafficking; 1,25 dihydroxyvitamin D 3Intestinal calcium absorption is a critical step in the maintenance of calcium homeostasis [Fleet, 2006]. It occurs by both paracellular and transcellular pathways [Bronner, 2003;Hoenderop et al., 2005]. The transcellular calcium absorption pathway is an active process that is regulated by the active form of vitamin D, 1,25 dihydroxyvitamin D 3 (1,25(OH) NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript of critical proteins: calbindin D 9k (CaBPD9k), the transient receptor vanelloid family member 6 (TRPV6), and the plasma membrane calcium ATPase 1b (PMCA1b) [Fleet et al., 2002;Song et al., 2003b;Fleet, 2006].The actions of 1,25(OH) 2 D 3 are mediated by the vitamin D receptor (VDR), a transcription factor that belongs to nuclear hormone receptor superfamily [Haussler et al., 1998]. The deletion of VDR in the enterocyte results in a 70% reduction in intestinal calcium absorption efficiency that is coincident with a significant reduction in CaBPD9k, TRPV6, and PMCA1b gene expression [Van Cromphaut et al., 2001;Song et al., 2003a].Previous research shows that binding of 1,25(OH) 2 D 3 to VDR in the cytoplasm of cells stimulates heterodimerization of VDR with RXR and the redistribution of the VDR-RXR-hormone complex to the nucleus [Barsony et al., 1990;Michigami et al., 1999;Racz and Barsony, 1999;Sunn et al., 2001]. The nuclear import of the VDR-RXR-hormone complex is active [Racz and Barsony, 1999;Miyauchi ...

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“…Effect of U0126 on DNA Binding and Subcellular Localization-If active RXR is the limiting factor in MC3T3-E1 cells, then treatment with U0126 should enhance VDR binding to DNA as the VDR/RXR heterodimer binds more stably to DNA than does a VDR dimer (57). Thus, to determine whether U0126 treatment altered DNA binding, nuclear extracts were prepared from MC3T3-E1 and HeLa cells treated with U0126 or not in the presence or absence of 1,25-D and EMSA were performed.…”

Section: Differential Regulation Of Vdr Activity In Mc3t3-e1 Cells Ismentioning

confidence: 99%

The Functional Consequences of Cross-talk between the Vitamin D Receptor and ERK Signaling Pathways Are Cell-specific

Narayanan

Sepúlveda

Falzon

et al. 2004

Journal of Biological Chemistry

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(8), and other cellular and physiological processes. Many of the actions of 1,25-D are mediated by an intracellular receptor, the vitamin D receptor (VDR), a member of the steroid/thyroid receptor superfamily of ligandregulated transcription factors (9, 10). The activity of VDR is dependent not only on the concentration of receptor and hormone but also on its heterodimer partner, retinoid X receptor (RXR), and the coactivator proteins that bind to the VDR and facilitate transcription of target genes (11).In addition to its actions as a modulator of transcription through activation of the VDR, 1,25-D can rapidly activate cell signaling cascades independent of a requirement for transcription (12-14). The means by which 1,25-D induces these changes has not been fully elucidated. Rapid activation of extracellular signal-regulated kinases, ERK1/ERK2 in NB4 promyelocytic leukemia cells can be induced not only by 1,25-D, but also by analogs that are unable to activate VDR, suggesting the possibility of a separate receptor (15). Antibodies to a membrane protein identified by Nemere et al. (16) block the ability of 1,25-D to induce rapid calcium uptake and activation of PKC in cartilage cells. VDRϪ/Ϫ osteoblasts take up calcium and activate PKC similar to the wild-type osteoblasts, implicating proteins other than VDR in these actions (17). In contrast, Gniadecki (18) has described activation of ERK through 1,25-D-induced activation of Raf as a result of interactions between VDR and the adaptor protein Shc. VDR-null osteoblasts do not exhibit ion channel responses in response to 1,25-D (13) and Erben et al. (14) have reported that deletion of the VDR DNA binding domain also eliminates non-genomic responses. Thus some of the rapid actions of 1,25-D may be dependent upon VDR, whereas others are not.Nuclear receptor family members including VDR and RXR as well as many of their coactivators, are phosphoproteins whose activities are also regulated by cell signaling pathways (19 -27). Thus 1,25-D can modulate VDR activity both through direct binding to VDR as well as by altering the kinase activities within the cell (9,11,12,28). Although VDR has not been reported to be a substrate for ERK, RXR␣ (one of the three RXR isoforms) (29) is phosphorylated by ERK, as are some of the VDR coactivators including SRC-1 (30).To better understand the functional interactions between VDR and the ERK signaling pathway, we sought to determine whether 1,25-D activates ERK in the osteoblastic cell lines, MG-63 and MC3T3-E1, and to evaluate the effects of ERK on VDR activity. We found that 1,25-D rapidly induced ERK activity and that this activation persisted at 24 h in both cell lines. Surprisingly, the effects of ERK activation on VDR activity in the two cell lines were very different. Overexpression of Raf-1 (an upstream activator of ERK) reduced VDR activity in MC3T3-E1 cells, but stimulated activity in MG-63 cells.

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Retinoid X Receptor Is a Nonsilent Major Contributor to Vitamin D Receptor-Mediated Transcriptional Activation

Cited by 80 publications

References 23 publications

Retinoids induce cytochrome P450 3A4 through RXR/VDR-mediated pathway

Retinoids induce cytochrome P450 3A4 through RXR/VDR-mediated pathway

Nucleo‐cytoplasmic cycling of the vitamin D receptor in the enterocyte‐like cell line, Caco‐2

The Functional Consequences of Cross-talk between the Vitamin D Receptor and ERK Signaling Pathways Are Cell-specific

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