Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Pulmonary alveolar type II cells have been shown to be a possible target for the secosteroid hormone, 1alpha,25-dihydroxyvitamin D3 [1alpha,25(OH)2D3], during perinatal transition. At present, there is great interest to isolate and identify the metabolites of 1alpha,25(OH)2D3 produced in its target tissues and to determine the contribution of each individual metabolite of 1alpha,25(OH)2D3 to the final expression of the pleiotropic actions attributed to 1alpha,25(OH)2D3. Of all the known metabolites of 1alpha,25(OH)2D3, 1alpha,25(OH)2-3-epi-D3 has gained most attention as it is produced only in specific tissues and possesses significant activity in tissues in which it is produced. Furthermore, in vivo studies indicate that this metabolite when compared to 1alpha,25(OH)2D3 is less calcemic. Therefore, we performed the present study to identify production of 1alpha,25(OH)2-3-epi-D3 in alveolar type II cells, and to evaluate its effect on surfactant synthesis. We incubated NCI-H441 cells, an alveolar type II cell line, with 1alpha,25(OH)2D3 and demonstrated that these cells metabolize 1alpha,25(OH)2D3 to various previously well-characterized polar metabolites, and to a less polar metabolite which was unequivocally identified as 1alpha,25(OH)2-3-epi-D3 by GC/MS and HPLC analysis. Further, biological activity studies in H441 cells indicated that 1alpha,25(OH)2-3-epi-D3 possesses significant activity in terms of its ability: (i) to increase surfactant phospholipid synthesis, (ii) to induce surfactant SP-B mRNA gene expression, and (iii) to increase surfactant SP-B protein synthesis. However, the activity of 1alpha,25(OH)2-3-epi-D3 when compared to 1alpha,25(OH)2D3 in generating VDR-mediated transcriptional activity in ROS 17/2.8 cells transfected with human osteocalcin VDRE/growth hormone gene construct, was significantly reduced. The high metabolic stability of 1alpha,25(OH)2-3-epi-D3, as previously proposed by us, may be a possible explanation for the high in vitro activity in spite of the reduced VDR-mediated transcriptional activity. In summary, we report for the first time the pathways of 1alpha,25(OH)2D3 metabolism in pulmonary alveolar type II cells and indicate that 1alpha,25(OH)2-3-epi-D3, a natural intermediary metabolite of 1alpha,25(OH)2D3 possesses significant activity in stimulating surfactant synthesis in alveolar type II cells.
Mol Genet Metab 2002 May
PMID:1Alpha,25-dihydroxy-3-epi-vitamin D3, a natural metabolite of 1alpha,25-dihydroxy vitamin D3: production and biological activity studies in pulmonary alveolar type II cells. 1217 80

All biologic responses to vitamin D are now known to arise as a consequence of the metabolism of this seco-steroid into its two principal biologically active metabolites 1alpha,25(OH)(2)-vitamin D(3) (1ALPHA;,25(OH)(2)D(3)) and 24R,25(OH)(2)-vitamin D(3) (24R,25(OH)(2)D(3)). 1alpha,25(OH)(2)D(3) is the dominant metabolite and produces a wide array of biological responses via interacting both with the classical vitamin D nuclear receptor (VDR(nuc)) that regulates gene transcription in over 30 target organs and with a putative cell membrane receptor (VDR(mem1,25)) that mediates rapid (within seconds to minutes) biological responses. Ligand occupancy of VDR(mem1,25) is linked to signal transduction systems that can mediate the opening of Ca(2+) and chloride voltage gated channels as well as activation of MAP-kinase. MAP-kinase activation in some cells containing VDR(mem1,25)+VDR(nuc) then results in "cross-talk" from VDR(mem1,25) to VDR(nuc) which modulates transactivation of 1alpha,25(OH)(2)D(3) responsive gene promoters. The 24R,25(OH)(2)D(3) metabolite has been shown to be an essential hormone for the process of bone fracture healing. The activity of the enzyme responsible for the production of 24R,25(OH)(2)D(3), the renal 25(OH)D-24-hydroxylase, becomes elevated within 4-11 days after imposition of a tibial fracture, thereby increasing the blood concentrations of 24R,25(OH)(2)D(3) by threefold. The 24R,25(OH)(2)D(3) likely initiates its biological responses via binding to the ligand binding domain of a second cell membrane receptor, the VDR(mem24,25), which is stereospecific for 24R,25(OH)(2)D(3) in comparison with 24S,25(OH)(2)D(3) and 1alpha,25(OH)(2)D(3). This report summarizes the status of several current research frontiers in this arena of the vitamin D endocrine system.
Mol Cell Endocrinol 2002 Nov 29
PMID:Update on biological actions of 1alpha,25(OH)2-vitamin D3 (rapid effects) and 24R,25(OH)2-vitamin D3. 1243 90

Thyroid hormones are important regulators of bone development and metabolism. We have demonstrated that tri-iodothyronine (T3) increased and 1,25-dihydroxyvitamin D3 (1,25D3) attenuated the T3-stimulated expression of osteocalcin (OCN) in the osteoblast-like cell line MC3T3-E1. By means of transfection of promoter-reporter gene constructs we investigated the basal and the regulated transcription of this gene by both hormones. We found that a 0.67 kbp and a 1.3 kbp fragment of the mouse OCN OG2 promoter containing two Runx2 binding sites were significantly more active than a smaller fragment containing only one Runx2 binding site. The longer promoter fragments showed a higher reporter gene expression when the transfected cells were treated with 10(-7) M T3. This expression was attenuated by 1,25D3 dose-dependently. These fragments contain a sequence homologue to the recently identified binding site for the 1,25D3 receptor (VDR) in the rat OCN promoter. Deletion of a part of the promoter containing this VDR response element-like sequence (VDRE) resulted in a higher basal expression but abrogated the regulation by T3 and 1,25D3. Electrophoretic mobility shift assays revealed that the deleted sequence was able to bind both in vitro-translated chicken thyroid hormone receptor (TR) and proteins from nuclear extracts that reacted with an antiserum against TR. From these data we conclude that the VDRE-like sequence of the OG2 promoter contains a thyroid hormone response element.
J Mol Endocrinol 2003 Feb
PMID:1,25-Dihydroxyvitamin D3 inhibits thyroid hormone-induced osteocalcin expression in mouse osteoblast-like cells via a thyroid hormone response element. 1258 Jul 60

Taking advantage of the "working draft" of the human genome and the MIT shotgun assembly of the mouse genome, we performed a comparative promoter analysis of human RefSeq mRNA (sequences from GenBank's RefSeq database). By combining this analysis with a transcription factor (TF) binding site analysis using a TRANSFAC position weight matrix (PWM) search, 86% of non-specific TF sites were removed. Using a set of genes that are regulated by parathyroid hormone (PTH), a statistical analysis was performed on the conserved TF binding sites among a set of eight human and mouse genes. From among the eight genes tested, we obtained a set of 31 TFs, suggesting possible roles for associated genes in PTH-mediated pathways. All three known PTH-responsive TFs (AP1, RUNX2, CREB) were correctly predicted by this analysis as well as two other potential TFs (VDR and CEBP Delta). Additionally, a model was made to describe the TF site characteristic module of PTH-regulated genes. This model was then used to search all human RefSeq gene promoters with established human-mouse ortholog relationships to identify other PTH-regulated genes. This comparative approach combined with statistical analysis proved to be sufficiently specific to decipher critical TFs involved in PTH-regulated pathways.
J Mol Biol 2003 Mar 07
PMID:Comparative promoter analysis and its application in analysis of PTH-regulated gene expression. 1259 47

1,25-Dihydroxyvitamin D(3) (1,25D(3)), the active metabolite of vitamin D(3), inhibits breast cancer cell growth in vivo and in vitro. To examine mechanisms of 1,25D(3) induced growth arrest and apoptosis, cell lines were established from DMBA induced mammary tumors derived from vitamin D(3) receptor knockout (VDRKO) and wild type (WT) mice. Two VDRKO (KO240, KO288) and two WT (WT145, WT276) cell lines were selected and characterized. All four cell lines express cytokeratins indicative of an epithelial origin, as well as vimentin, which is expressed in many transformed cell lines. The tumorigenicity of the cells was confirmed in vivo as all four cell lines form estrogen responsive tumors in nude mice. Both WT cell lines express the VDR protein and are sensitive to growth inhibition by 1,25D(3) at doses as low as 1 nM. Flow cytometric analysis indicated that 1,25D(3) induces G(0)/G(1) arrest and apoptosis in the WT cell lines. In contrast, both cell lines established from tumors that developed in VDRKO mice lack VDR mRNA and protein. Cells from WT mice exhibit 1,25D(3) inducible transcriptional activity, as measured by reporter gene assays, but cells from VDRKO mice do not. Cells from VDRKO mice are also completely resistant to 1,25D(3) mediated growth arrest and apoptosis over the range of 0.01-100 nM 1,25D(3). VDRKO cells are also resistant to the synthetic vitamin D(3) analogs EB1089 and CB1093 that are more potent growth inhibitors than 1,25D(3) in WT cells. This data conclusively demonstrate that the induction of cell cycle arrest and apoptosis in breast cancer cells by 1,25D(3), EB1089 and CB1093 is dependent on the nuclear VDR. Cells lacking VDR remain sensitive to growth arrest mediated by 9-cis retinoic acid, a ligand for the retinoid x receptor which can heterodimerize with the VDR. Sensitivity to apoptosis induced by the DNA damaging agent etoposide is not altered in VDRKO cells, indicating that VDR ablation does not impair apoptotic pathways in general. All four cell lines display equal sensitivity to tamoxifen induced growth arrest. These estrogen responsive, transformed cell lines which differentially express the VDR provide a novel model system for identification of the mechanisms by which 1,25D(3) regulates proliferation and apoptosis in breast cancer cells.
Mol Cell Endocrinol 2003 Feb 28
PMID:Characterization of mammary tumor cell lines from wild type and vitamin D3 receptor knockout mice. 1264

1,25-Dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) interacts with the Vitamin D(3) receptor (VDR) to modulate proliferation and apoptosis in a variety of cell types, including breast cancer cells. In this review, we discuss three issues related to the role of the VDR in growth control: first, whether mammary glands lacking VDR exhibit abnormal growth; second, whether the VDR is essential for induction of apoptosis by 1,25(OH)(2)D(3); and third, whether VDR up-regulation can sensitize cells to 1,25(OH)(2)D(3). Studies from our laboratory have demonstrated that mammary glands from VDR knockout (VDR KO) mice exhibit accelerated growth and branching during puberty, pregnancy and lactation as compared to wild-type (WT) mice. In addition, involution after weaning, a process driven by epithelial cell apoptosis, proceeds at a slower rate in VDR KO mice compared to WT mice. Using cells isolated from VDR KO and WT mice, we report that both normal and transformed mammary cells derived from WT mice are growth inhibited by 1,25(OH)(2)D(3), however, cells derived from VDR KO mice are completely unresponsive to 1,25(OH)(2)D(3). In human breast cancer cells, we have identified a variety of agents, including steroid hormones, phytoestrogens and growth factors, that up-regulate VDR expression and enhance sensitivity to 1,25(OH)(2)D(3)-mediated growth inhibition. Collectively, these studies support a role for 1,25(OH)(2)D(3) and the VDR in negative growth regulation of both normal mammary gland and breast cancer cells.
J Steroid Biochem Mol Biol 2002 Dec
PMID:Impact of the Vitamin D3 receptor on growth-regulatory pathways in mammary gland and breast cancer. 1265 Jul 4

1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)), a steroid hormone derived from Vitamin D(3), is a negative growth regulator of breast cancer cells, and Vitamin D(3) analogs represent a novel treatment approach for human cancer. Elucidation of Vitamin D(3) receptor (VDR) regulation may reveal strategies to sensitize cancer cells to the effects of 1,25-dihydroxyvitamin D(3) and Vitamin D(3) analogs. We have previously characterized an estrogen responsive promoter region (800 bp upstream of exon 1c) in the human VDR gene, and the present studies examined regulation of this VDR promoter region by two phytoestrogens, resveratrol (present in red wine) and genistein (present in soy). We transiently transfected a VDR promoter luciferase construct into the estrogen receptor (ER) positive human breast cancer cell lines T47D and MCF-7, and treated with 0.4-4 microM resveratrol or 5-500 nM genistein. Both phytoestrogens up-regulated the transcription of the VDR promoter, as measured by reporter gene activity, approximately two-fold compared to vehicle treated cells. Co-treatment with the anti-estrogen tamoxifen (TAM) in T47D cells and transfection in an estrogen receptor negative breast cancer cell line demonstrated that the effects of phytoestrogens on the VDR promoter are dependent on estrogen receptor. Resveratrol and genistein also increased VDR protein expression as detected by Western blotting. Treatment with resveratrol had no effect on cell number or cell cycle profile, while treatment with genistein increased cell number. Because resveratrol could up-regulate VDR without increasing breast cancer cell growth, we hypothesized that resveratrol mediated increase in VDR expression would sensitize breast cancer cells to the effects of 1,25-dihydroxyvitamin D(3) and Vitamin D(3) analogs. In support of this hypothesis, both T47D and MCF-7 cells pre-treated with resveratrol exhibited increased VDR mediated transactivation of a Vitamin D(3) responsive promoter compared to cells pre-treated with vehicle. In addition, co-treatment with resveratrol enhanced the growth inhibitory effects of 1,25-dihydroxyvitamin D(3) and the Vitamin D(3) analog EB1089. These data support the concept that dietary factors, such as phytoestrogens, may impact on breast cancer cell sensitivity to Vitamin D(3) analogs through regulation of the VDR promoter.
J Steroid Biochem Mol Biol 2003 Feb
PMID:Phytoestrogen regulation of a Vitamin D3 receptor promoter and 1,25-dihydroxyvitamin D3 actions in human breast cancer cells. 1271 Sep 98

Vitamin D(3) compounds offer an alternative approach to anti-hormonal therapies for human breast cancer. 1,25-Dihydroxyvitamin D(3) (1,25-(OH)(2)D(3)) acts through the nuclear Vitamin D(3) receptor (VDR), a phosphoprotein and ligand-dependent transcription factor. Our lab has shown that 1,25-(OH)(2)D(3) induces apoptosis in MCF-7 cells by disruption of mitochondrial function which is associated with Bax translocation to mitochondria, cytochrome c release, and production of reactive oxygen species (ROS). TPA, a protein kinase C (PKC) activator, does not induce cytochrome c release or Bax translocation, thus demonstrating that it has no effect on mitochondria and apoptosis on its own. However, when the MCF-7(D(3)Res) cells (a Vitamin D(3)-resistant variant) are treated with 1,25-(OH)(2)D(3) in the presence of TPA, the cells displayed apoptotic morphology and redistribution of both cytochrome c and Bax. TPA pretreatment greatly enhances 1,25-(OH)(2)D(3) stimulated 24-hydroxylase luciferase activity and VDR protein expression, although transactivation is lower in the MCF-7(D(3)Res) cells compared to the parental cell line. The observation that the phorbol ester TPA sensitizes the Vitamin D(3)-resistant variant to the effects of 1,25-(OH)(2)D(3) suggests an important role for phosphorylation in dictating sensitivity to Vitamin D(3)-mediated apoptosis. This study demonstrates that the effects of 1,25-(OH)(2)D(3) on mitochondrial disruption might be sensitized through activators of PKC.
J Steroid Biochem Mol Biol 2003 Feb
PMID:Induction of apoptosis by 1,25-dihydroxyvitamin D3 in MCF-7 Vitamin D3-resistant variant can be sensitized by TPA. 1271 Oct 4

Cells in the epithelial rest of Malassez (ERM cells) express calbindin D28k (CB); however, the hormonal regulation of CB in ERM cells remains to be elucidated. We investigated the immunohistochemical localization of CB and 1,25-dihydroxyvitamin D3 receptor (VDR) during root formation of mouse molar teeth in order to clarify whether the expression of CB in ERM cells is dependent on vitamin D. At the early stage of root formation (postnatal (PN) days 10-14), both CB- and VDR-immunoreactive cells were observed intermittently along the root surface. In the apical portion, almost all CB-immunoreactive cells showed VDR immunoreactivity; however, VDR-immunoreactive cells in the most apical portion were immunonegative for CB. In the middle and cervical portions, the distributions of the two proteins were completely different. At the late stage of root formation (PN28d) and in adult animals, CB immunoreactivity was distributed in cells found along the acellular cementum at the bifurcation region, as well as between the dentin and cellular cementum in the apical portion (although these lacked immunoreactivity for VDR). The present results indicate that CB expression in newly disrupted cells from Hertwig's epithelial root sheath occurs in a vitamin-D dependent manner, whereas the expression of CB in mature ERM cells may be independent of vitamin D.
Anat Rec A Discov Mol Cell Evol Biol 2003 Aug
PMID:Immunolocalization of calbindin D28k and vitamin D receptor during root formation of murine molar teeth. 1284 6

The multi-subunit, human CRSP coactivator-also known as Mediator (Med)-regulates transcription by mediating signals between enhancer-bound factors (activators) and the core transcriptional machinery. Interestingly, different activators are known to bind distinct subunits within the CRSP/Med complex. We have isolated a stable, endogenous CRSP/Med complex (CRSP/Med2) that specifically lacks both the Med220 and the Med70 subunits. The three-dimensional structure of CRSP/Med2 was determined to 31 A resolution using electron microscopy and single-particle reconstruction techniques. Despite lacking both Med220 and Med70, CRSP/Med2 displays potent, activator-dependent transcriptional coactivator function in response to VP16, Sp1, and Sp1/SREBP-1a in vitro using chromatin templates. However, CRSP/Med2 is unable to potentiate activated transcription from a vitamin D receptor-responsive promoter, which requires interaction with Med220 for coactivator recruitment, whereas VDR-directed activation by CRSP/Med occurs normally. Thus, it appears that CRSP/Med may be regulated by a combinatorial assembly mechanism that allows promoter-selective function upon exchange of specific coactivator targets.
Mol Cell 2004 Jun 04
PMID:Structure and function of CRSP/Med2; a promoter-selective transcriptional coactivator complex. 1517 62


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>