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

1 ,25-Dihydroxyvitamin D3 [1,25-(OH)2D3] negatively regulates expression of the avian PTH (aPTH) gene transcript, and a vitamin D response element (VDRE) near the promoter of the aPTH gene had previously been identified. The present report assessed whether the negative activity imparted by the aPTH VDRE could be converted to a positive transcriptional response through selective mutations introduced into the element. The tested sequences were derived from individual and combined mutations to 2 bp in the 3'-half of the direct repeat element, GGGTCAggaGGGTGT. Cold competition experiments using mutant and wild-type oligonucleotides in the mobility shift assay revealed minor differences in the ability of any of these sequences to compete for binding to a heterodimer complex comprised of recombinant proteins. Ethylation interference footprint analysis for each of the mutants produced unique patterns over the 3'-half-sites that were distinct from the weak, wild-type footprint. Transcriptional outcomes evaluated from a chloramphenicol acetyltransferase reporter construct utilizing the aPTH promoter found that the individual T-->A mutant produced an attenuated negative transcriptional response while the G-->C mutant resulted in a reproducibly weak positive transcriptional outcome. The double mutant, however, yielded a 4-fold increase in transcription, similar to the 7-fold increase observed from an analogous construct using the human osteocalcin VDRE. UV light crosslinking to gapped oligonucleotides assessed the polarity of heterodimer binding to the wild-type and double mutant sequences and was consistent with the vitamin D receptor preferentially binding to the 5'-half of both elements. Finally, DNA affinity chromatography was used to immobilize heterodimer complexes bound to the wild-type and double mutant sequences as bait to identify proteins that may preferentially interact with these DNA-bound heterodimers. This analysis revealed the presence of a p160 protein that specifically interacted with the heterodimer bound to the wild-type VDRE, but was absent from complexes bound to response elements associated with positive transcriptional activity. Thus, the sequence of the individual VDRE appears to play an active role in dictating transcriptional responses that may be mediated by altering the ability of a vitamin D receptor heterodimer to interact with accessory factor proteins.
Mol Endocrinol 1999 Mar
PMID:Turning a negative into a positive: vitamin D receptor interactions with the avian parathyroid hormone response element. 1007 2

1,25-Dihydroxyvitamin D3 (D3) exerts its effects by binding to and activating nuclear vitamin D3 receptors (VDRs) that regulate transcription of target genes. We have investigated regulation of VDR levels in human skin in vivo and in cultured human keratinocytes. Quantitative ligand-binding analysis revealed that human skin expressed approximately 220 VDRs per cell, which bound D3 with high affinity [(dissociation constant (Kd) = 0.22 nM]. In human skin nuclear extracts, VDR exclusively bound to DNA containing vitamin D3 response elements as heterodimers with retinoid X receptors. Topical application of D3 to human skin elevated VDR protein levels 2-fold, as measured by both ligand-binding and DNA-binding assays. In contrast, the D3 analog calcipotriene had no effect on VDR levels. Topical D3 had no effect on VDR mRNA, indicating that D3 either stimulated synthesis and/or inhibited degradation of VDRs. To investigate this latter possibility, recombinant VDRs were incubated with skin lysates in the presence or absence of D3. The presence of D3 substantially protected VDRs against degradation by human skin lysates. VDR degradation was inhibited by proteasome inhibitors, but not lysosome or serine protease inhibitors. In cultured keratinocytes, D3 or proteasome inhibitors increased VDR protein without affecting VDR mRNA levels. In cells, VDR was ubiquitinated and this ubiquitination was inhibited by D3. Proteasome inhibitors in combination with D3 enhanced VDR-mediated gene expression, as measured by induction of vitamin D3 24-hydroxylase mRNA in cultured keratinocytes. Taken together, our findings indicate that low VDR levels are maintained, in part, through ubiquitin/proteasome-mediated degradation and that low VDR levels limit D3 signaling. D3 exerts dual positive influences on its nuclear receptor, simultaneously stimulating VDR transactivation activity and retarding VDR degradation.
Mol Endocrinol 1999 Oct
PMID:1,25-Dihydroxyvitamin D3 increases nuclear vitamin D3 receptors by blocking ubiquitin/proteasome-mediated degradation in human skin. 1051 70

In the rat thyroid FRTL-5 cell line calcitriol, the biologically most active of the naturally occurring vitamin D metabolites, attenuates both TSH-stimulated cAMP production and the effects of cAMP. Calcitriol treatment abolishes the upregulation of the TSHR number occurring in cells cultivated in the absence of TSH. In addition, the level of G(i-2)alpha increases, which may further attenuate the transmembrane signaling of TSH and facilitate the effects of IGFs. The effect of cAMP on PKAI stimulation is inhibited by increasing the level of the PKA subunit RIIbeta. Regulation of TSHR, G(i-2)alpha and RIIbeta is associated with altered cell proliferation and differentiation in several cells and tissues. Effects of calcitriol on these proteins indicate how the vitamin D endocrine system may regulate cAMP signaling in both classical and nonclassical target tissues.
Crit Rev Biochem Mol Biol 1999
PMID:Vitamin D: a hormonal regulator of the cAMP signaling pathway. 1056 77

Changes in circulating levels of insulin-like growth factors (IGF) and IGF-binding proteins (IGFBP) have been related to prostate cancer, but the nature and the significance of this relationship remains elusive. Recent reports suggest that modulation of the production of IGFBP-3 by retinoids may affect growth of breast and prostate tumor cells. In the present study we explored whether androgens (R1881), retinoids (all-trans- and 9-cis-retinoic acid: atRA and 9cRA), deltanoids (1alpha,25-dihydroxycholecalciferol: VD3) and thyroid hormone (triiodothyronine: T3) influence the production of IGFBPs by LNCaP prostatic adenocarcinoma cells and whether the observed changes affect tumor cell growth. Northern blot experiments demonstrated that LNCaP cells express IGFBP-2, -3, -4 and (to a small extent) -5. IGFBP-4 and -5 were not measurably affected by the mentioned agonists. At a growth promoting concentration (10(-10) M), R1881 increased IGFBP-2 transcript levels two- to three-fold and this effect was neutralized by atRA and VD3. Similar effects could not be demonstrated, however, at the protein level using Western ligand blotting. R1881 decreased and atRA increased the mRNA levels of IGFBP-3 and these effects were confirmed by Western ligand blotting and by radioimmunoassay. The effects of atRA were mimicked by 9cRA and by a specific RAR agonist but not by a RXR agonist. VD3 and T3 had no significant effect on IGFBP-3 secretion but respectively enhanced or decreased the effect of 9cRA. The effects of retinoids required high concentrations (10(-6)-10(-5) M) that also induced growth inhibition. R1881, however, decreased IGFBP-3 at growth promoting (10(-10) M) as well as at growth inhibitory (10(-8) M) concentrations. Moreover, under serum-free conditions, we were unable to demonstrate any growth modulating effect of IGFBP-3. It is concluded that several agonists acting by nuclear receptors affect IGFBP-3 secretion by LNCaP cells but that the functional significance of these changes warrants further investigation.
Mol Cell Endocrinol 1999 Sep 10
PMID:Androgens decrease and retinoids increase the expression of insulin-like growth factor-binding protein-3 in LNcaP prostatic adenocarcinoma cells. 1058 Aug 34

(23S)-25-dehydro-1alpha-Dihydroxyvitamin D3-26,23-lactone (TEI-9647; MK) has been reported to antagonize the 1alpha,25-dihydroxyvitamin D3 nuclear receptor (VDR)- mediated increase in transcriptional activity. Using a transient transfection system incorporating the osteocalcin VDRE (vitamin D response element) in Cos-1 cells, we found that 20 nM MK antagonizes VDR-mediated transcription by 50% when driven by 1 nM 1alpha,25(OH)2D3. Four analogs of 1alpha,25(OH)2D3, also at 1 nM, were antagonized 25 to 39% by 20 nM MK. However, analogs with 16-ene/23-yne or 20-epi modifications, which have a significantly lower agonist ED50 for the VDR than 1alpha,25(OH)2D3, were antagonized by 20 nM MK only at 100 pM or 10 pM, respectively. One possible mechanism for antagonism is that the 25-dehydro alkene of MK might covalently bind the ligand-binding site of the VDR rendering it inactive. Utilization of a ligand exchange assay, however, demonstrated that MK bound to VDR is freely exchanged with 1alpha,25(OH)2D3 in vitro. These data support the apparent correlation between VDR transcriptional activation by agonists and the effective range of MK antagonism by competition. Furthermore, protease sensitivity analysis of MK bound to VDR indicates the presence of a unique conformational change in the VDR ligand-binding domain, showing a novel doublet of VDR fragments centered at 34 kDa, whereas 1alpha,25(OH)2D3 as a ligand produces only a single 34-kDa fragment. In comparison, the natural metabolite 1alpha,25-dihydroxyvitamin D3-26,23-lactone yields only the 30-kDa fragment that is produced by all ligands to varying degrees. Collectively, these results support that MK is a potent partial antagonist of the VDR for 1alpha,25(OH)2D3 and its analogs when in appropriate excess of the agonist.
Mol Endocrinol 2000 Nov
PMID:25-Dehydro-1alpha-hydroxyvitamin D3-26,23S-lactone antagonizes the nuclear vitamin D receptor by mediating a unique noncovalent conformational change. 1107 12

1,25-Dihydroxyvitamin D(3), thought to be a physiological regulator of epidermal keratinocyte growth and differentiation, also elicits the complete differentiative program in vitro, with expression of various genes/proteins characteristic of both early and late differentiation. 1,25-Dihydroxyvitamin D(3) functions by interacting with an intracellular receptor that binds to DNA at vitamin D response elements (VDRE) thereby affecting transcription. 1,25-Dihydroxyvitamin D(3) has been demonstrated to alter the expression of several enzymes involved in signal transduction, and presumably this is the mechanism through which the hormone regulates differentiation. It has recently been shown that 1,25-dihydroxyvitamin D(3) specifically increases the expression/activity of phospholipase D-1, an enzyme that hydrolyzes phospholipids to generate lipid messengers, such as diacylglycerol (DAG). DAG, in turn, is known to activate several members of the protein kinase C (PKC) family. It has been proposed that this signaling pathway mediates late differentiation events in epidermal keratinocytes. In this article the data supporting a role for PKC and phospholipase D in keratinocyte differentiation, as well as in the pathogenesis of skin diseases, are reviewed and a model is proposed for the signaling pathways that regulate this process upon exposure to 1,25-dihydroxyvitamin D(3).
Mol Cell Endocrinol 2001 May 25
PMID:1,25-Dihydroxyvitamin D(3), phospholipase D and protein kinase C in keratinocyte differentiation. 1137 32

Dahl salt-sensitive rats, but not salt-resistant rats, develop hypertension in response to high salt intake. We have previously shown an inverse relationship between plasma 25-hydroxyvitamin D (25-OHD) concentration and blood pressure of Dahl salt-sensitive rats during high salt intake. In this study, we report on the relationship between high salt intake and plasma 24,25-dihydroxyvitamin D (24,25-(OH)(2)D) concentration of Dahl salt-sensitive and salt-resistant rats. Rats were fed a high salt diet (8%) and sacrificed at day 2, 7, 14, 21, and 28. Plasma 24,25-(OH)(2)D concentrations of salt-sensitive rats were reduced to 50% of that at baseline at day 2-when blood pressure and plasma 25-OHD concentration were unchanged, but 25-OHD content in the kidney was 81% of that at baseline. Plasma 24,25-(OH)(2)D concentration was reduced further to 10% of that at baseline from day 7 to 14 of high salt intake, a reduction that was prevented in rats switched to a low salt (0.3%) diet at day 7. Exogenous 24,25-dihydroxycholecalciferol (24,25-(OH)(2)D(3)), administered at a level that increased plasma 24,25-(OH)(2)D concentration to five times normal, did not attenuate the salt-induced hypertension of salt-sensitive rats. Plasma 24,25-(OH)(2)D concentration of salt-resistant rats was gradually reduced to 50% of that at baseline at day 14 and returned to baseline value at day 28 of high salt intake. We conclude that the decrease in plasma 24,25-(OH)(2)D concentration in salt-sensitive rats during high salt intake is caused by decreased 25-OHD content in the kidney and also by another unidentified mechanism.
J Steroid Biochem Mol Biol 2002 Mar
PMID:Plasma 24,25-dihydroxyvitamin D concentration of Dahl salt-sensitive rats decreases during high salt intake. 1194 16

Little is known about the effect of enzyme replacement therapy (ERT) on the bone abnormalities in Gaucher disease. Splenectomized Gaucher patients tend to suffer the most severe skeletal complications. We hypothesized that vitamin D supplementation would act synergistically with glucocerebrosidase infusions to increase bone density in splenectomized Gaucher patients. In a 24-month study, 29 splenectomized Gaucher patients were randomized to three groups: Group 1, calcitriol (1,25-dihydroxyvitamin D3; 0.25-3.0 microg/day) alone for the first 6 months with the addition of ceredase/cerezyme at 60 IU/kg every 2 weeks during months 7-12; Group 2, calcitriol together with ceredase/cerezyme at 60 IU/kg every 2 weeks during months 1-6; and Group 3, enzyme only at 60 IU/kg body wt every 2 weeks. In all three groups, enzyme dose was halved after the first 6 months of therapy. The primary outcome measure was bone mineral density of the lumbar spine measured by single-energy quantitative CT. Bone density by single-energy CT (P = 0.001) and by dual-energy CT (P = 0.06) declined overall, but there was no significant difference between the groups. Calcitriol had no significant effect on bone density. Fat fraction in lumbar spine increased (P = 0.000) and skeletal MRI scores improved. Bone-specific alkaline phosphatase (P = 0.002) and serum osteocalcin increased (P = 0.008), while blood cyclic AMP and urinary deoxypyridinoline did not change appreciably. Hemoglobin, platelet counts, and liver volume significantly improved. We conclude that ERT alone, or in combination with calcitriol, cannot repair the bone composition in splenectomized adult Gaucher patients. Alternatively, measuring trabecular bone density may be an inadequate marker of clinical efficacy for treating skeletal involvement in Gaucher disease.
Blood Cells Mol Dis
PMID:Decreased bone density in splenectomized Gaucher patients receiving enzyme replacement therapy. 1206 24

Calcitriol [1alpha,25-dihydroxyvitamin D3] is the natural ligand of the vitamin D receptor (VDR). Using cultured prostate cancer (PC) cell lines, LN-CaP and ALVA-31, we studied the effects of 1alpha,25(OH)2-Vitamin D3 (VD3) on expression of several apoptosis-regulating proteins including: (a) Bcl-2 family proteins (Bcl-2, Bcl-X(L), Mcl-1, Bax, and Bak); (b) the heat shock protein 70-binding protein BAG1L; and (c) IAP family proteins (XIAP, cIAP1, and cIAP2). VD3 induced decreases in levels of antiapoptotic proteins Bcl-2, Bcl-X(L), and Mcl-1, BAG1L, XIAP, cIAP1, and cIAP2 (without altering proapoptotic Bax and Bak) in association with increases in apoptosis. In contrast to VDR-expressing LN-CaP and ALVA-31 cells, VDR-deficient prostate cancer line Du-145 demonstrated no changes in apoptosis protein expression after treatment with VD3. In sensitive PC cell lines, VD3 activates downstream effector protease, caspase-3, and upstream initiator protease caspase-9, the apical protease in the mitochondrial ("intrinsic") pathway for apoptosis, but not caspase-8, an initiator caspase linked to an alternative ("extrinsic") apoptosis pathway triggered by cytokine receptors. VD3 induced declines in antiapoptotic proteins and also stimulated cytochrome c release from mitochondria by a caspase-independent mechanism. Moreover, apoptosis induction by VD3 was suppressed by overexpressing Bcl-2, a known blocker of cytochrome c release, whereas the caspase-8 suppressor CrmA afforded little protection. Thus, VD3 is capable of inhibiting expression of multiple antiapoptotic proteins in VDR-expressing prostate cancer cells, leading to activation of the mitochondrial pathway for apoptosis.
Mol Cancer Ther 2002 Jul
PMID:Apoptosis induction by 1alpha,25-dihydroxyvitamin D3 in prostate cancer. 1247 63

1,25-Dihydroxyvitamin D3 (1,25D3) exhibits potent antitumor activity in the murine squamous cell carcinoma (SCC) SCCVII/SF, and the combination of 1,25D3 with cisplatin (1,25D3/cisplatin) demonstrates even greater activity. Because these agents possess different mechanisms of cytotoxicity, studies were initiated to define the mechanism by which the combination displays enhanced activity. Median dose-effect analysis demonstrates that 1,25D3 and cisplatin act synergistically to inhibit SCC growth. When SCC cells were treated with 1,25D3 (10 nM) and/or cisplatin (0.5 microg/ml), greater caspase-3 activation was observed for the combination than for either agent alone. This suggests that the enhanced cytotoxicity is, at least in part, due to greater induction of apoptosis. No alterations in cellular platinum concentration or platinum-DNA adducts were observed for 1,25D3/cisplatin cotreatment compared with cisplatin treatment alone. Effects of the combination on cisplatin and 1,25D3 signaling pathways in adherent (nonapoptotic) and floating (apoptotic) cells were explored. Cisplatin induced p53 and its downstream targets, p21(Cip1) (p21) and Bax, in both cell populations. In contrast, 1,25D3 reduced p53, p21, and Bax to nearly undetectable levels in adherent cells. In the floating cells, 1,25D3 reduced levels of p53 and p21, but Bax expression was maintained at control levels. Expression of these proteins in cells treated with 1,25D3/cisplatin was similar to treatment with 1,25D3 alone. The two agents also had divergent effects on survival and stress signaling pathways. Phospho-extracellular signal-regulated kinase 1/2 and phospho-Jun levels increased after treatment with cisplatin but decreased after treatment with 1,25D3 and 1,25D3/cisplatin. Moreover, cisplatin decreased levels of mitogen-activated protein kinase kinase kinase (MEKK-1), whereas 1,25D3 up-regulated MEKK-1, and 1,25D3/cisplatin further up-regulated MEKK-1. We propose that the increased cytotoxicity for 1,25D3/cisplatin results from cisplatin enhancement of 1,25D3-induced apoptotic signaling through MEKK-1.
Mol Cancer Ther 2002 Aug
PMID:Cisplatin potentiates 1,25-dihydroxyvitamin D3-induced apoptosis in association with increased mitogen-activated protein kinase kinase kinase 1 (MEKK-1) expression. 1249 15


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