Mark R Haussler

Interests

Research

A. Vitamin D action and receptors for the vitamin D hormone that regulate gene transcription; B. Osteoporosis and other metabolic bone diseases related to calcium and phosphorus homeostasis, emphasizing the function of the vitamin D hormone, FGF23, and sex steroids in bone remodeling; C. Nutrigenomics: the participation of novel, nutritionally generated ligands, as well as common polymorphisms in the vitamin D receptor gene, in the prevention of cancers of the colon, prostate and skin, as well as playing a role in hair growth.

Teaching

Biochemistry, Endocrinology, Gene Expression, Metabolism, Molecular Pathology, Pharmacology, Physiology, Signal Transduction, and the Gastrointestinal, Musculoskeletal, Renal and Reproductive Systems

Courses

No activities entered.

Scholarly Contributions

Chapters

• Haussler, M. R., Saini, R. K., Sabir, M. S., Dussik, C. M., Khan, Z., Whitfield, G. K., Griffin, K. P., Kaneko, I., & Jurutka, P. W. (2016). Vitamin D nutrient-gene interactions and healthful aging. In Molecular Basis of Nutrition and Aging, First Edition(pp 449-471). San Diego: Elsevier Academic Press.
• Haussler, M. R., Whitfield, G. K., Haussler, C. A., Sabir, M. S., Khan, Z., Sandoval, R., & Jurutka, P. W. (2016). 1,25-Dihydroxyvitamin D and klotho: a tale of two renal hormones coming of age. In Vitamins and Hormones - Volume 100(pp 165-231). London: Elsevier.
• Jurutka, P. W., Whitfield, G. K., Forster, R., Batie, S., Lee, J., & Haussler, M. R. (2013). Vitamin D: A fountain of youth in gene regulation.. In Vitamin D: Oxidative Stress, Immunity, and Aging(pp 3-35). New York: CRC Press.
• Whitfield, G. K., Jurutka, P. W., Haussler, C. A., Hsieh, J. -., Barthel, T. K., Jacobs, E. T., Encinas Dominguez, C., Thatcher, M. L., & Haussler, M. R. (2005). Nuclear vitamin D receptor: Structure-function, molecular control of gene transcription and novel bioactions.. In Vitamin D, Second Edition(pp 219-261). San Diego: Elsevier Academic Press.

Journals/Publications

• Haussler, M. R., Whitfield, G. K., Jurutka, P. W., Jacobs, E. T., Batie, S. F., Sabir, M. S., Lee, J. H., & Dampf Stone, A. -. (2015). Resveratrol potentiates vitamin D and nuclear receptor signaling. Journal of Cellular Biochemistry, 116, 1130-1143. doi:DOI 10.1002/jcb.25070
• Kaneko, I., Sabir, M. S., Dussik, C. M., Whitfield, G. K., Karrys, A., Hsieh, J., Haussler, M. R., Meyer, M. B., Pike, J. W., & Jurutka, P. W. (2015). 1,25-Dihydroxyvitamin D regulates expression of the tryptophan hydroxylase 2 and leptin genes: implication for behavioral influences of vitamin D. FASEB journal : official publication of the Federation of American Societies for Experimental Biology, 29(9), 4023-35.
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  To investigate vitamin D-related control of brain-expressed genes, candidate vitamin D responsive elements (VDREs) at -7/-10 kb in human tryptophan hydroxylase (TPH)2 were probed. Both VDREs bound the vitamin D receptor (VDR)-retinoid X receptor (RXR) complex and drove reporter gene transcription in response to 1,25-dihydroxyvitamin D3 (1,25D). Brain TPH2 mRNA, encoding the rate-limiting enzyme in serotonin synthesis, was induced 2.2-fold by 10 nM 1,25D in human U87 glioblastoma cells and 47.8-fold in rat serotonergic RN46A-B14 cells. 1,25D regulation of leptin (Lep), encoding a serotoninlike satiety factor, was also examined. In mouse adipocytes, 1,25D repressed leptin mRNA levels by at least 84%, whereas 1,25D induced leptin mRNA 15.1-fold in human glioblastoma cells. Chromatin immunoprecipitation sequencing analysis of the mouse Lep gene in response to 1,25D revealed a cluster of regulatory sites (cis-regulatory module; CRM) at -28 kb that 1,25D-dependently docked VDR, RXR, C/EBPβ, and RUNX2. This CRM harbored 3 VDREs and single C/EBPβ and RUNX2 sites. Therefore, the expression of human TPH2 and mouse Lep are governed by 1,25D, potentially via respective VDREs located at -7/-10 kb and -28 kb. These results imply that vitamin D affects brain serotonin concentrations, which may be relevant to psychiatric disorders, such as autism, and may control leptin levels and affect eating behavior.
• Kaneko, I., Saini, R. K., Griffin, K. P., Whitfield, G. K., Haussler, M. R., & Jurutka, P. W. (2015). FGF23 gene regulation by 1,25-dihydroxyvitamin D: opposing effects in adipocytes and osteocytes. The Journal of endocrinology, 226(3), 155-66.
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  In a closed endocrine loop, 1,25-dihydroxyvitamin D3 (1,25D) induces the expression of fibroblast growth factor 23 (FGF23) in bone, with the phosphaturic peptide in turn acting at kidney to feedback repress CYP27B1 and induce CYP24A1 to limit the levels of 1,25D. In 3T3-L1 differentiated adipocytes, 1,25D represses FGF23 and leptin expression and induces C/EBPβ, but does not affect leptin receptor transcription. Conversely, in UMR-106 osteoblast-like cells, FGF23 mRNA concentrations are upregulated by 1,25D, an effect that is blunted by lysophosphatidic acid, a cell-surface acting ligand. Progressive truncation of the mouse FGF23 proximal promoter linked in luciferase reporter constructs reveals a 1,25D-responsive region between -400 and -200  bp. A 0.6  kb fragment of the mouse FGF23 promoter, linked in a reporter construct, responds to 1,25D with a fourfold enhancement of transcription in transfected K562 cells. Mutation of either an ETS1 site at -346  bp, or an adjacent candidate vitamin D receptor (VDR)/Nurr1-element, in the 0.6  kb reporter construct reduces the transcriptional activity elicited by 1,25D to a level that is not significantly different from a minimal promoter. This composite ETS1-VDR/Nurr1 cis-element may function as a switch between induction (osteocytes) and repression (adipocytes) of FGF23, depending on the cellular setting of transcription factors. Moreover, experiments demonstrate that a 1 kb mouse FGF23 promoter-reporter construct, transfected into MC3T3-E1 osteoblast-like cells, responds to a high calcium challenge with a statistically significant 1.7- to 2.0-fold enhancement of transcription. Thus, the FGF23 proximal promoter harbors cis elements that drive responsiveness to 1,25D and calcium, agents that induce FGF23 to curtail the pathologic consequences of their excess.
• Haussler, M. R., Hsieh, J. -., Whitfield, G. K., Estess, R. C., Kaneko, I. -., & Jurutka, P. W. (2014). Vitamin D receptor-mediated control of Soggy, Wise, and Hairless gene expression in keratinocytes. Journal of Endocrinology, 220(2), 165-178.
• Haussler, M. R., Whitfield, G. K., Austin, H. R., Jurutka, P. W., Hoss, E., Batie, S. F., & Moffet, E. W. (2014). Regulation of Late Cornified Envelope Genes Relevant to Psoriasis Risk by Plant-derived Cyanidin. Biochem. Biophys. Res. Commun., 443(4), 1275-1279.
• Haussler, M. R., Whitfield, G. K., Kaneko, I., Haussler, C. A., Hsieh, D., Hsieh, J., & Jurutka, P. W. (2013). Molecular mechanisms of vitamin D action. Calcified Tissue International, 92(2).
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  The hormonal metabolite of vitamin D, 1alpha,25-dihydroxyvitamin D(3) (1,25D), initiates biological responses via binding to the vitamin D receptor (VDR). When occupied by 1,25D, VDR interacts with the retinoid X receptor (RXR) to form a heterodimer that binds to vitamin D responsive elements in the region of genes directly controlled by 1,25D. By recruiting complexes of either coactivators or corepressors, ligand-activated VDR-RXR modulates the transcription of genes encoding proteins that promulgate the traditional functions of vitamin D, including signaling intestinal calcium and phosphate absorption to effect skeletal and calcium homeostasis. Thus, vitamin D action in a particular cell depends upon the metabolic production or delivery of sufficient concentrations of the 1,25D ligand, expression of adequate VDR and RXR coreceptor proteins, and cell-specific programming of transcriptional responses to regulate select genes that encode proteins that function in mediating the effects of vitamin D. For example, 1,25D induces RANKL, SPP1 (osteopontin), and BGP (osteocalcin) to govern bone mineral remodeling; TRPV6, CaBP(9k), and claudin 2 to promote intestinal calcium absorption; and TRPV5, klotho, and Npt2c to regulate renal calcium and phosphate reabsorption. VDR appears to function unliganded by 1,25D in keratinocytes to drive mammalian hair cycling via regulation of genes such as CASP14, S100A8, SOSTDC1, and others affecting Wnt signaling. Finally, alternative, low-affinity, non-vitamin D VDR ligands, e.g., lithocholic acid, docosahexaenoic acid, and curcumin, have been reported. Combined alternative VDR ligand(s) and 1,25D/VDR control of gene expression may delay chronic disorders of aging such as osteoporosis, type 2 diabetes, cardiovascular disease, and cancer.
• Hoss, E., Austin, H. R., Batie, S. F., Jurutka, P. W., Haussler, M. R., & Whitfield, G. K. (2013). Control of late cornified envelope genes relevant to psoriasis risk: upregulation by 1,25-dihydroxyvitamin D3 and plant-derived delphinidin. Archives of Dermatological Research, 305(10), 867-878.
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  Psoriasis is a chronic inflammatory skin disease featuring abnormal keratinocyte proliferation and differentiation. A genetic risk factor for psoriasis (PSORS4) is a deletion of LCE3B and LCE3C genes encoding structural proteins in terminally differentiated keratinocytes. Because analogs of 1,25-dihydroxyvitamin D3 (1,25D) are used in psoriasis treatment, we hypothesized that 1,25D acts via the vitamin D receptor (VDR) to upregulate expression of LCE 3A/3D/3E genes, potentially mitigating the absence of LCE3B/LCE3C gene products. Results in a human keratinocyte line, HaCaT, suggested that 1,25D, low affinity VDR ligands docosahexaenoic acid and curcumin, along with a novel candidate ligand, delphinidin, induce LCE transcripts as monitored by qPCR. Further experiments in primary human keratinocytes preincubated with 1.2 mM calcium indicated that 1,25D and 10 microM delphinidin upregulate all five LCE3 genes (LCE3A-E). Competition binding assays employing radiolabeled 1,25D revealed that delphinidin binds VDR weakly (IC50=1mM). However, 20 microM delphinidin was capable of upregulating a luciferase reporter gene in a VDRE-dependent manner in a transfected keratinocyte cell line (KERTr). These results are consistent with a scenario in which delphinidin is metabolized to an active compound that then stimulates LCE3 transcription in a VDR/VDRE-dependent manner. We propose that upregulation of LCE genes may be part of the therapeutic effect of 1,25D to ameliorate psoriasis by providing sufficient LCE proteins, especially in individuals missing the LCE3B and 3C genes. Results with delphinidin further suggest that this compound or its metabolite(s) might offer an alternative to 1,25D in psoriasis therapy.
• Jacobs, E. T., Van Pelt, C., Forster, R. E., Zaidi, W., Hibler, E. A., Galligan, M. A., Haussler, M. R., & Jurutka, P. W. (2013). CYP24A1 and CYP27B1 polymorphisms modulate vitamin D metabolism in colon cancer cells. Cancer Research, 73(8).
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  Vitamin D is a well-studied agent for cancer chemoprevention and treatment. Its chief circulating metabolite, 25-hydroxyvitamin D, is converted into the active hormone 1,25-dihydroxyvitamin D (1,25D) by the cytochrome P450 enzyme CYP27B1 in kidney and other tissues. 1,25D is then deactivated by CYP24A1 and ultimately catabolized. Colorectal carcinoma cells express CYP27B1 and CYP24A1 that locally regulate 1,25D with potential implications for its impact on carcinogenesis. While 1,25D inhibits cancer growth, the effects of polymorphic variations in genes encoding proteins involved in 1,25D homeostasis are poorly understood. Using an RXR-VDR mammalian two-hybrid (M2H) biologic assay system, we measured vitamin D metabolite uptake and activation of the vitamin D receptor (VDR) pathway in colon cancer cells that expressed one of five CYP27B1 single-nucleotide polymorphisms (SNP) or four CYP24A1 SNPs. Compared with the wild-type control, four of five CYP27B1 SNPs reduced enzymatic activity, whereas one (V166L) increased activity. For CYP24A1, all tested SNPs reduced enzyme activity. Quantitative real-time PCR analyses supported the results of M2H experiments. The observed SNP-directed variation in CYP functionality indicated that vitamin D homeostasis is complex and may be influenced by genetic factors. A comprehensive understanding of 1,25D metabolism may allow for a more personalized approach toward treating vitamin D-related disorders and evaluating risk for carcinogenesis.
• Saini, R. K., Kaneko, I., Jurutka, P. W., Forster, R., Hsieh, A., Hsieh, J., Haussler, M. R., & Whitfield, G. K. (2013). 1,25-Dihydroxyvitamin D(3) regulation of fibroblast growth factor-23 expression in bone cells: evidence for primary and secondary mechanisms modulated by leptin and interleukin-6. Calcified Tissue International, 92(4).
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  Fibroblast growth factor-23 (FGF23) is a circulating hormone that acts to correct hyperphosphatemic states by inhibiting renal phosphate reabsorption and to prevent hypervitaminosis D by feedback repressing 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) biosynthesis. FGF23 gene expression in the osteoblast/osteocyte is induced by the nuclear vitamin D receptor (VDR) bound to 1,25(OH)2D3, but cycloheximide sensitivity of this induction suggests that it may occur largely via secondary mechanisms requiring cooperating transcription factors. We therefore sought to identify 1,25(OH)2D3-regulated transcription factors that might impact FGF23 expression. Although neither leptin nor interleukin-6 (IL-6) alone affects FGF23 expression, leptin treatment was found to potentiate 1,25(OH)2D3 upregulation of FGF23 in UMR-106 cells, whereas IL-6 treatment blunted this upregulation. Genomic analyses revealed conserved binding sites for STATs (signal transduction mediators of leptin and IL-6 action) along with transcription factor ETS1 in human and other mammalian FGF23 genes. Further, STAT3, STAT1, ETS1, and VDR mRNAs were induced in a dose-dependent manner by 1,25(OH)2D3 in UMR-106 cells. Bioinformatic analysis identified nine potential VDREs in a genomic interval containing human FGF23. Six of the putative VDREs were capable of mediating direct transcriptional activation of a heterologous reporter gene when bound by a 1,25(OH)2D3-liganded VDR complex. A model is proposed wherein 1,25(OH)2D3 upregulates FGF23 production directly via multiple VDREs and indirectly via induction of STAT3, ETS1, and VDR transcription factors that are then activated via cell surface and intracellular signaling to cooperate in the induction of FGF23 through DNA looping and generation of euchromatin architecture.
• Haussler, M. R., Whitfield, G. K., Kaneko, I., Forster, R., Saini, R., Hsieh, J., Haussler, C. A., & Jurutka, P. W. (2012). The role of vitamin D in the FGF23, klotho, and phosphate bone-kidney endocrine axis. Reviews in Endocrine & Metabolic Disorders, 13(1).
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  1,25-dihydroxyvitamin D (1,25D), through association with the nuclear vitamin D receptor (VDR), exerts control over a novel endocrine axis consisting of the bone-derived hormone FGF23, and the kidney-expressed klotho, CYP27B1, and CYP24A1 genes, which together prevent hyperphosphatemia/ectopic calcification and govern the levels of 1,25D to maintain bone mineral integrity while promoting optimal function of other vital tissues. When occupied by 1,25D, VDR interacts with RXR to form a heterodimer that binds to VDREs in the region of genes directly controlled by 1,25D (e.g., FGF23, klotho, Npt2c, CYP27B1 and CYP24A1). By recruiting complexes of comodulators, activated VDR initiates a series of events that induces or represses the transcription of genes encoding proteins such as: the osteocyte-derived hormone, FGF23; the renal anti-senescence factor and protein co-receptor for FGF23, klotho; other mediators of phosphate transport including Npt2a/c; and vitamin D hormone metabolic enzymes, CYP27B1 and CYP24A1. The mechanism whereby osteocytes are triggered to release FGF23 is yet to be fully defined, but 1,25D, phosphate, and leptin appear to play major roles. The kidney responds to FGF23 to elicit CYP24A1-catalyzed detoxification of the 1,25D hormone while also repressing both Npt2a/c to mediate phosphate elimination and CYP27B1 to limit de novo 1,25D synthesis. Comprehension of these skeletal and renal actions of 1,25D should facilitate the development of novel mimetics to prevent ectopic calcification, chronic renal and vascular disease, and promote healthful aging.
• Forster, R. E., Jurutka, P. W., Hsieh, J., Haussler, C. A., Lowmiller, C. L., Kaneko, I., Haussler, M. R., & Kerr Whitfield, G. (2011). Vitamin D receptor controls expression of the anti-aging klotho gene in mouse and human renal cells. Biochemical and biophysical research communications, 414(3).
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  Isoforms of the mammalian klotho protein serve as membrane co-receptors that regulate renal phosphate and calcium reabsorption. Phosphaturic effects of klotho are mediated in cooperation with fibroblast growth factor receptor-1 and its FGF23 ligand. The vitamin D receptor and its 1,25-dihydroxyvitamin D(3) ligand are also crucial for calcium and phosphate regulation at the kidney and participate in a feedback loop with FGF23 signaling. Herein we characterize vitamin D receptor-mediated regulation of klotho mRNA expression, including the identification of vitamin D responsive elements (VDREs) in the vicinity of both the mouse and human klotho genes. In keeping with other recent studies of vitamin D-regulated genes, multiple VDREs control klotho expression, with the most active elements located at some distance (-31 to -46 kb) from the klotho transcriptional start site. We therefore postulate that the mammalian klotho gene is up-regulated by liganded VDR via multiple remote VDREs. The phosphatemic actions of 1,25-dihydroxyvitamin D(3) are thus opposed via the combined phosphaturic effects of FGF23 and klotho, both of which are upregulated by the liganded vitamin D receptor.
• Haussler, M. R., Jurutka, P. W., Mizwicki, M., & Norman, A. W. (2011). Vitamin D receptor (VDR)-mediated actions of 1α,25(OH)₂vitamin D₃: genomic and non-genomic mechanisms. Best practice & research. Clinical endocrinology & metabolism, 25(4).
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  The conformationally flexible secosteroid, 1α,25(OH)₂vitamin D₃ (1α,25(OH)₂D₃) initiates biological responses via binding to the vitamin D receptor (VDR). The VDR contains two overlapping ligand binding sites, a genomic pocket (VDR-GP) and an alternative pocket (VDR-AP), that respectively bind a bowl-like ligand configuration (gene transcription) or a planar-like ligand shape (rapid responses). When occupied by 1α,25(OH)₂D₃, the VDR-GP interacts with the retinoid X receptor to form a heterodimer that binds to vitamin D responsive elements in the region of genes directly controlled by 1α,25(OH)₂D₃. By recruiting complexes of either coactivators or corepressors, activated VDR modulates the transcription of genes encoding proteins that promulgate the traditional genomic functions of vitamin D, including signaling intestinal calcium and phosphate absorption to effect skeletal and calcium homeostasis. 1α,25(OH)₂D₃/VDR control of gene expression and rapid responses also delays chronic diseases of aging such as osteoporosis, cancer, type-1 and -2 diabetes, arteriosclerosis, vascular disease, and infection.
• Bartik, L., Whitfield, G. K., Kaczmarska, M., Lowmiller, C. L., Moffet, E. W., Furmick, J. K., Hernandez, Z., Haussler, C. A., Haussler, M. R., & Jurutka, P. W. (2010). Curcumin: a novel nutritionally derived ligand of the vitamin D receptor with implications for colon cancer chemoprevention. The Journal of nutritional biochemistry, 21(12).
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  The nuclear vitamin D receptor (VDR) mediates the actions of 1,25-dihydroxyvitamin D(3) (1,25D) to regulate gene transcription. Recently, the secondary bile acid, lithocholate (LCA), was recognized as a novel VDR ligand. Using reporter gene and mammalian two-hybrid systems, immunoblotting, competitive ligand displacement and quantitative real-time PCR, we identified curcumin (CM), a turmeric-derived bioactive polyphenol, as a likely additional novel ligand for VDR. CM (10(-5) M) activated transcription of a luciferase plasmid containing the distal vitamin D responsive element (VDRE) from the human CYP3A4 gene at levels comparable to 1,25D (10(-8) M) in transfected human colon cancer cells (Caco-2). While CM also activated transcription via a retinoid X receptor (RXR) responsive element, activation of the glucocorticoid receptor (GR) by CM was negligible. Competition binding assays with radiolabeled 1,25D confirmed that CM binds directly to VDR. In mammalian two-hybrid assays employing transfected Caco-2 cells, CM (10(-5) M) increased the ability of VDR to recruit its heterodimeric partner, RXR, and steroid receptor coactivator-1 (SRC-1). Real-time PCR studies revealed that CM-bound VDR can activate VDR target genes CYP3A4, CYP24, p21 and TRPV6 in Caco-2 cells. Numerous studies have shown chemoprotection by CM against intestinal cancers via a variety of mechanisms. Small intestine and colon are important VDR-expressing tissues where 1,25D has known anticancer properties that may, in part, be elicited by activation of CYP-mediated xenobiotic detoxification and/or up-regulation of the tumor suppressor p21. Our results suggest the novel hypothesis that nutritionally-derived CM facilitates chemoprevention via direct binding to, and activation of, VDR.
• Egan, J. B., Thompson, P. A., Vitanov, M. V., Bartik, L., Jacobs, E. T., Haussler, M. R., Gerner, E. W., & Jurutka, P. W. (2010). Vitamin D receptor ligands, adenomatous polyposis coli, and the vitamin D receptor FokI polymorphism collectively modulate beta-catenin activity in colon cancer cells. Molecular carcinogenesis, 49(4).
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  The activity of beta-catenin, commonly dysregulated in human colon cancers, is inhibited by the vitamin D receptor (VDR), and this mechanism is postulated to explain the putative anti-cancer activity of vitamin D metabolites in the colon. We investigated the effect of a common FokI restriction site polymorphism (F/f) in the human VDR gene as well as the effect of anti-tumorigenic 1,25-dihydroxyvitamin D(3) (1,25D) and pro-tumorigenic lithocholic acid (LCA) VDR ligands on beta-catenin transcriptional activity. Furthermore, the influence of a major regulatory protein of beta-catenin, the APC tumor suppressor gene, on VDR-dependent inhibition of beta-catenin activity was examined. We report herein that beta-catenin-mediated transcription is most effectively suppressed by the VDR FokI variant F/M4 when 1,25D is limiting. Using Caco-2 colorectal cancer (CRC) cells, it was observed that VDR ligands, 1,25D and LCA, both suppress beta-catenin transcriptional activity, though 1,25D exhibited significantly greater inhibition. Moreover, 1,25D, but not LCA, suppressed endogenous expression of the beta-catenin target gene DKK-4 independent of VDR DNA-binding activity. These results support beta-catenin sequestration away from endogenous gene targets by 1,25D-VDR. This activity is most efficiently mediated by the FokI gene variant F/M4, a VDR allele previously associated with protection against CRC. Interestingly, we found the inhibition of beta-catenin activity by 1,25D-VDR was significantly enhanced by wild-type APC. These results reveal a previously unrecognized role for 1,25D-VDR in APC/beta-catenin cross talk. Collectively, these findings strengthen evidence favoring a direct effect on the Wnt-signaling molecule beta-catenin as one anti-cancer target of 1,25D-VDR action in the colorectum.
• Haussler, M. R., Haussler, C. A., Whitfield, G. K., Hsieh, J., Thompson, P. D., Barthel, T. K., Bartik, L., Egan, J. B., Wu, Y., Kubicek, J. L., Lowmiller, C. L., Moffet, E. W., Forster, R. E., & Jurutka, P. W. (2010). The nuclear vitamin D receptor controls the expression of genes encoding factors which feed the "Fountain of Youth" to mediate healthful aging. The Journal of steroid biochemistry and molecular biology, 121(1-2).
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  The nuclear vitamin D receptor (VDR) binds 1,25-dihydroxyvitamin D3 (1,25D), its high affinity renal endocrine ligand, to signal intestinal calcium and phosphate absorption plus bone remodeling, generating a mineralized skeleton free of rickets/osteomalacia with a reduced risk of osteoporotic fractures. 1,25D/VDR signaling regulates the expression of TRPV6, BGP, SPP1, LRP5, RANKL and OPG, while achieving feedback control of mineral ions to prevent age-related ectopic calcification by governing CYP24A1, PTH, FGF23, PHEX, and klotho transcription. Vitamin D also elicits numerous intracrine actions when circulating 25-hydroxyvitamin D3, the metabolite reflecting vitamin D status, is converted to 1,25D locally by extrarenal CYP27B1, and binds VDR to promote immunoregulation, antimicrobial defense, xenobiotic detoxification, anti-inflammatory/anticancer actions and cardiovascular benefits. VDR also affects Wnt signaling through direct interaction with beta-catenin, ligand-dependently blunting beta-catenin mediated transcription in colon cancer cells to attenuate growth, while potentiating beta-catenin signaling via VDR ligand-independent mechanisms in osteoblasts and keratinocytes to function osteogenically and as a pro-hair cycling receptor, respectively. Finally, VDR also drives the mammalian hair cycle in conjunction with the hairless corepressor by repressing SOSTDC1, S100A8/S100A9, and PTHrP. Hair provides a shield against UV-induced skin damage and cancer in terrestrial mammals, illuminating another function of VDR that facilitates healthful aging.
• Hsieh, J., Slater, S. A., Whitfield, G. K., Dawson, J. L., Hsieh, G., Sheedy, C., Haussler, C. A., & Haussler, M. R. (2010). Analysis of hairless corepressor mutants to characterize molecular cooperation with the vitamin D receptor in promoting the mammalian hair cycle. Journal of cellular biochemistry, 110(3).
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  The mammalian hair cycle requires both the vitamin D receptor (VDR) and the hairless (Hr) corepressor, each of which is expressed in the hair follicle. Hr interacts directly with VDR to repress VDR-targeted transcription. Herein, we further map the VDR-interaction domain to regions in the C-terminal half of Hr that contain two LXXLL-like pairs of motifs known to mediate contact of Hr with the RAR-related orphan receptor alpha and with the thyroid hormone receptor, respectively. Site-directed mutagenesis indicates that all four hydrophobic motifs are required for VDR transrepression by Hr. Point mutation of rat Hr at conserved residues corresponding to natural mutants causing alopecia in mice (G985W and a C-terminal deletion DeltaAK) and in humans (P95S, C422Y, E611G, R640Q, C642G, N988S, D1030N, A1040T, V1074M, and V1154D), as well as alteration of residues in the C-terminal Jumonji C domain implicated in histone demethylation activity (C1025G/E1027G and H1143G) revealed that all Hr mutants retained VDR association, and that transrepressor activity was selectively abrogated in C642G, G985W, N988S, D1030N, V1074M, H1143G, and V1154D. Four of these latter Hr mutants (C642G, N988S, D1030N, and V1154D) were found to associate normally with histone deacetylase-3. Finally, we identified three regions of human VDR necessary for association with Hr, namely residues 109-111, 134-201, and 202-303. It is concluded that Hr and VDR interact via multiple protein-protein interfaces, with Hr recruiting histone deacetylases and possibly itself catalyzing histone demethylation to effect chromatin remodeling and repress the transcription of VDR target genes that control the hair cycle.
• Haussler, M. R., Haussler, C. A., Bartik, L., Whitfield, G. K., Hsieh, J., Slater, S., & Jurutka, P. W. (2008). Vitamin D receptor: molecular signaling and actions of nutritional ligands in disease prevention. Nutrition reviews, 66(10 Suppl 2).
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  The human vitamin D receptor (VDR) is a key nuclear receptor that binds nutritionally derived ligands and exerts bioeffects that contribute to bone mineral homeostasis, detoxification of exogenous and endogenous compounds, cancer prevention, and mammalian hair cycling. Liganded VDR modulates gene expression via heterodimerization with the retinoid X receptor and recruitment of coactivators or corepressors. VDR interacts with the corepressor hairless (Hr) to control hair cycling, an action independent of the endocrine VDR ligand, 1,25-dihydroxyvitamin D(3). We report novel dietary ligands for VDR including curcumin, gamma-tocotrienol, and essential fatty acid derivatives that likely play a role in the bioactions of VDR.
• Barthel, T. K., Mathern, D. R., Whitfield, G. K., Haussler, C. A., Hopper, H. A., Hsieh, J., Slater, S. A., Hsieh, G., Kaczmarska, M., Jurutka, P. W., Kolek, O. I., Ghishan, F. K., & Haussler, M. R. (2007). 1,25-Dihydroxyvitamin D3/VDR-mediated induction of FGF23 as well as transcriptional control of other bone anabolic and catabolic genes that orchestrate the regulation of phosphate and calcium mineral metabolism. The Journal of steroid biochemistry and molecular biology, 103(3-5).
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  1,25-Dihydroxyvitamin D(3) (1,25D) is known primarily as a regulator of calcium, but 1,25D also promotes phosphate absorption from intestine, reabsorption from kidney, and bone mineral resorption. FGF23 is a newly discovered phosphaturic hormone that, like PTH, lowers serum phosphate by inhibiting renal reabsorption via Npt2a. We show that 1,25D strongly upregulates FGF23 in bone. FGF23 then represses 1alpha-OHase activity in kidney, thus preventing spiraling induction of FGF23 by 1,25D. We also report that LRP5, Runx2, TRPV6, and Npt2c, all anabolic toward bone, and RANKL, which is catabolic, are transcriptionally regulated by 1,25D. This coordinated regulation together with that of FGF23 and PTH allows 1,25D to play a central role in maintaining calcium and phosphate homeostasis and bone metabolism. In the cases of LRP5, Runx2, TRPV6, and Npt2c we show that transcriptional regulation results at least in part from direct binding of VDR near the relevant gene promoter. Finally, because 1,25D induces FGF23, and FGF23 in turn represses 1,25D synthesis, a reciprocal relationship is established with FGF23 indirectly curtailing 1,25D-mediated intestinal absorption and counterbalancing renal reabsorption of phosphate. This newly revealed FGF23/1,25D/Pi axis is comparable in significance to phosphate and bone metabolism as the PTH/1,25D/Ca axis is to calcium homeostasis.
• Jurutka, P. W., Bartik, L., Whitfield, G. K., Mathern, D. R., Barthel, T. K., Gurevich, M., Hsieh, J. -., Kaczmarska, M., Haussler, C. A., & Haussler, M. R. (2007). Vitamin D receptor: key roles in bone mineral pathophysiology, molecular mechanism of action and novel nutritional ligands.. J. Bone Miner. Res., V2-V10.
• Jurutka, P. W., Bartik, L., Whitfield, G. K., Mathern, D. R., Barthel, T. K., Gurevich, M., Hsieh, J., Kaczmarska, M., Haussler, C. A., & Haussler, M. R. (2007). Vitamin D receptor: key roles in bone mineral pathophysiology, molecular mechanism of action, and novel nutritional ligands. Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research, 22 Suppl 2.
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  The vitamin D hormone, 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)], binds with high affinity to the nuclear vitamin D receptor (VDR), which recruits its retinoid X receptor (RXR) heterodimeric partner to recognize vitamin D responsive elements (VDREs) in target genes. 1,25(OH)(2)D(3) is known primarily as a regulator of calcium, but it also controls phosphate (re)absorption at the intestine and kidney. Fibroblast growth factor 23 (FGF23) is a phosphaturic hormone produced in osteoblasts that, like PTH, lowers serum phosphate by inhibiting renal reabsorption through Npt2a/Npt2c. Real-time PCR and reporter gene transfection assays were used to probe VDR-mediated transcriptional control by 1,25(OH)(2)D(3). Reporter gene and mammalian two-hybrid transfections, plus competitive receptor binding assays, were used to discover novel VDR ligands. 1,25(OH)(2)D(3) induces FGF23 78-fold in osteoblasts, and because FGF23 in turn represses 1,25(OH)(2)D(3) synthesis, a reciprocal relationship is established, with FGF23 indirectly curtailing 1,25(OH)(2)D(3)-mediated intestinal absorption and counterbalancing renal reabsorption of phosphate, thereby reversing hyperphosphatemia and preventing ectopic calcification. Therefore, a 1,25(OH)(2)D(3)-FGF23 axis regulating phosphate is comparable in importance to the 1,25(OH)(2)D(3)-PTH axis that regulates calcium. 1,25(OH)(2)D(3) also elicits regulation of LRP5, Runx2, PHEX, TRPV6, and Npt2c, all anabolic toward bone, and RANKL, which is catabolic. Regulation of mouse RANKL by 1,25(OH)(2)D(3) supports a cloverleaf model, whereby VDR-RXR heterodimers bound to multiple VDREs are juxtapositioned through chromatin looping to form a supercomplex, potentially allowing simultaneous interactions with multiple co-modulators and chromatin remodeling enzymes. VDR also selectively binds certain omega3/omega6 polyunsaturated fatty acids (PUFAs) with low affinity, leading to transcriptionally active VDR-RXR complexes. Moreover, the turmeric-derived polyphenol, curcumin, activates transcription of a VDRE reporter construct in human colon cancer cells. Activation of VDR by PUFAs and curcumin may elicit unique, 1,25(OH)(2)D(3)-independent signaling pathways to orchestrate the bioeffects of these lipids in intestine, bone, skin/hair follicle, and other VDR-containing tissues.
• Jacobs, E. T., Haussler, M. R., & Martínez, M. E. (2005). Vitamin D activity and colorectal neoplasia: a pathway approach to epidemiologic studies. Cancer epidemiology, biomarkers & prevention : a publication of the American Association for Cancer Research, cosponsored by the American Society of Preventive Oncology, 14(9).
• Jurutka, P. W., Thompson, P. D., Whitfield, G. K., Eichhorst, K. R., Hall, N., Dominguez, C. E., Hsieh, J., Haussler, C. A., & Haussler, M. R. (2005). Molecular and functional comparison of 1,25-dihydroxyvitamin D(3) and the novel vitamin D receptor ligand, lithocholic acid, in activating transcription of cytochrome P450 3A4. Journal of cellular biochemistry, 94(5).
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  The vitamin D receptor (VDR) binds to and mediates the effects of the 1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) hormone to alter gene transcription. A newly recognized VDR ligand is the carcinogenic bile acid, lithocholic acid (LCA). We demonstrate that, in HT-29 colon cancer cells, both LCA and 1,25(OH)(2)D(3) induce expression of cytochrome P450 3A4 (CYP3A4), an enzyme involved in cellular detoxification. We also show that LCA-VDR stimulates transcription of gene reporter constructs containing DR3 and ER6 vitamin D responsive elements (VDREs) from the human CYP3A4 gene. Utilizing gel mobility shift, pulldown, and mammalian two-hybrid assays, we observe that: (i) 1,25(OH)(2)D(3) enhances retinoid X receptor (RXR) heterodimerization with VDR more effectively than LCA, (ii) the 1,25(OH)(2)D(3)-liganded VDR-RXR heterodimer recruits full-length SRC-1 coactivator, whereas this interaction is minimal with LCA unless LXXLL-containing fragments of SRC-1 are employed, and (iii) both 1,25(OH)(2)D(3) and LCA enhance the binding of VDR to DRIP205/mediator, but unlike 1,25(OH)(2)D(3)-VDR, LCA-VDR does not interact detectably with NCoA-62 or TRIP1/SUG1, suggesting a different pattern of LCA-VDR comodulator association. Finally, residues in the human VDR (hVDR) ligand binding domain (LBD) were altered to create mutants unresponsive to 1,25(OH)(2)D(3)- and/or LCA-stimulated transactivation, identifying S237 and S225/S278 as critical for 1,25(OH)(2)D(3) and LCA action, respectively. Therefore, these two VDR ligands contact distinct residues in the binding pocket, perhaps generating unique receptor conformations that determine the degree of RXR and comodulator binding. We propose that VDR is a bifunctional regulator, with the 1,25(OH)(2)D(3)-liganded conformation facilitating high affinity endocrine actions, and the LCA-liganded configuration mediating local, lower affinity cellular detoxification by upregulation of CYP3A4 in the colon.
• Kolek, O. I., Hines, E. R., Jones, M. D., LeSueur, L. K., Lipko, M. A., Kiela, P. R., Collins, J. F., Haussler, M. R., & Ghishan, F. K. (2005). 1alpha,25-Dihydroxyvitamin D3 upregulates FGF23 gene expression in bone: the final link in a renal-gastrointestinal-skeletal axis that controls phosphate transport. American journal of physiology. Gastrointestinal and liver physiology, 289(6).
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  Fibroblast growth factor (FGF)23 is a phosphaturic hormone that decreases circulating 1alpha,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] and elicits hypophosphatemia, both of which contribute to rickets/osteomalacia. It has been shown recently that serum FGF23 increases after treatment with renal 1,25(OH)(2)D(3) hormone, suggesting that 1,25(OH)(2)D(3) negatively feedback controls its levels by inducing FGF23. To establish the tissue of origin and the molecular mechanism by which 1,25(OH)(2)D(3) increases circulating FGF23, we administered 1,25(OH)(2)D(3) to C57BL/6 mice. Within 24 h, these mice displayed a dramatic elevation in serum immunoreactive FGF23, and the expression of FGF23 mRNA in bone was significantly upregulated by 1,25(OH)(2)D(3), but there was no effect in several other tissues. Furthermore, we treated rat UMR-106 osteoblast-like cells with 1,25(OH)(2)D(3), and real-time PCR analysis revealed a dose- and time-dependent stimulation of FGF23 mRNA concentrations. The maximum increase in FGF23 mRNA was 1,024-fold at 10(-7) M 1,25(OH)(2)D(3) after 24-h treatment, but statistically significant differences were observed as early as 4 h after 1,25(OH)(2)D(3) treatment. In addition, using cotreatment with actinomycin D or cycloheximide, we observed that 1,25(OH)(2)D(3) regulation of FGF23 gene expression occurs at the transcriptional level, likely via the nuclear vitamin D receptor, and is dependent on synthesis of an intermediary transfactor. These results indicate that bone is a major site of FGF23 expression and source of circulating FGF23 after 1,25(OH)(2)D(3) administration or physiological upregulation. Our data also establish FGF23 induction by 1,25(OH)(2)D(3) in osteoblasts as a feedback loop between these two hormones that completes a kidney-intestine-bone axis that mediates phosphate homeostasis.
• Hines, E. R., Kolek, O. I., Jones, M. D., Serey, S. H., Sirjani, N. B., Kiela, P. R., Jurutka, P. W., Haussler, M. R., Collins, J. F., & Ghishan, F. K. (2004). 1,25-dihydroxyvitamin D3 down-regulation of PHEX gene expression is mediated by apparent repression of a 110 kDa transfactor that binds to a polyadenine element in the promoter. The Journal of biological chemistry, 279(45).
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  The PHEX gene encodes an endopeptidase expressed in osteoblasts that inactivates an uncharacterized peptide hormone, phosphatonin, which suppresses bone mineralization as well as renal phosphate reabsorption and vitamin D bioactivation. We demonstrate that 1alpha-25-dihydroxyvitamin D (1,25(OH)2D3), the, active renal vitamin D metabolite, decreases PHEX mRNA in the rat osteoblastic cell line, UMR-106, as well as in mouse calvaria. Promoter/reporter construct analysis of the murine PHEX gene in transfected UMR-106 cells localized the repressive effect of 1,25(OH)2D3 to the -133 to -74 bp region, and gel mobility shift experiments revealed that 1,25(OH)2D3 treatment of the cells diminished the binding of a nuclear protein(s) to a stretch of 17 adenines from bp -116 to -100 in the proximal PHEX promoter. Either overexpression of a dominant-negative vitamin D receptor (VDR) or deletion of this sequence of 17 A-T base pairs abolished the repressive effect of 1,25(OH)2D3 by attenuating basal promoter activity, indicating that this region mediates the 1,25(OH)2D3 response and is involved in basal transcription. South-western blot analysis and DNA affinity purification show that an unidentified 110 kDa nuclear protein binds to the poly(A) element. Because 1,25(OH)2D3-liganded VDR neither binds to the polyadenine region of the PHEX promoter nor directly influences the association of the 110 kDa transfactor, we conclude that 1,25(OH)2D3 indirectly decreases PHEX expression via VDR-mediated repression (or modification) of this novel transactivator. Thus, we have identified a cis-element required for PHEX gene transcription that participates in negative feedback control of PHEX expression and thereby modulates the actions of phosphatonin.
• Hsieh, J., Dang, H. T., Galligan, M. A., Whitfield, G. K., Haussler, C. A., Jurutka, P. W., & Haussler, M. R. (2004). Phosphorylation of human vitamin D receptor serine-182 by PKA suppresses 1,25(OH)2D3-dependent transactivation. Biochemical and biophysical research communications, 324(2).
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  The human vitamin D receptor (hVDR), which is a substrate for several protein kinases, mediates the actions of its 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) ligand to regulate gene expression. To determine the site, and functional impact, of cAMP-dependent protein kinase (PKA)-catalyzed phosphorylation of hVDR, we generated a series of C-terminally truncated and point mutant receptors. Incubation of mutant hVDRs with PKA and [gamma-32P]ATP, in vitro, or overexpressing them in COS-7 kidney cells labeled with [32P]orthophosphate, revealed that serine-182 is the predominant residue in hVDR phosphorylated by PKA. An aspartate substituted mutant (S182D), incorporating a negative charge to mimic phosphorylation, displayed only 50% of the transactivation capacity in response to 1,25(OH)2D3 of either wild-type or an S182A-altered hVDR. When the catalytic subunit of PKA was overexpressed, a similar reduction in wild-type but not S182D hVDR transactivity was observed. In a mammalian two-hybrid system, S182D bound less avidly than wild-type or S182A hVDR to the retinoid X receptor (RXR) heterodimeric partner that co-mediates vitamin D responsive element recognition and transactivation. These data suggest that hVDR serine-182 is a primary site for PKA phosphorylation, an event that leads to an attenuation of both RXR heterodimerization and resultant transactivation of 1,25(OH)2D3 target genes.
• Hsieh, J., Sisk, J. M., Jurutka, P. W., Haussler, C. A., Slater, S. A., Haussler, M. R., & Thompson, C. C. (2003). Physical and functional interaction between the vitamin D receptor and hairless corepressor, two proteins required for hair cycling. The Journal of biological chemistry, 278(40).
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  Both the vitamin D receptor (VDR) and hairless (hr) genes play a role in the mammalian hair cycle, as inactivating mutations in either result in total alopecia. VDR is a nuclear receptor that functions as a ligand-activated transcription factor, whereas the hairless gene product (Hr) acts as a corepressor of both the thyroid hormone receptor (TR) and the orphan nuclear receptor, RORalpha. In the present study, we show that VDR-mediated transactivation is strikingly inhibited by coexpression of rat Hr. The repressive effect of Hr is observed on both synthetic and naturally occurring VDR-responsive promoters and also when VDR-mediated transactivation is augmented by overexpression of its heterodimeric partner, retinoid X receptor. Utilizing in vitro pull down methods, we find that Hr binds directly to VDR but insignificantly to nuclear receptors that are not functionally repressed by Hr. Coimmunoprecipitation data demonstrate that Hr and VDR associate in a cellular milieu, suggesting in vivo interaction. The Hr contact site in human VDR is localized to the central portion of the ligand binding domain, a known corepressor docking region in other nuclear receptors separate from the activation function-2 domain. Coimmunoprecipitation and functional studies of Hr deletants reveal that VDR contacts a C-terminal region of Hr that includes motifs required for TR and RORalpha binding. Finally, in situ hybridization analysis of hr and VDR mRNAs in mouse skin demonstrates colocalization in cells of the hair follicle, consistent with a hypothesized intracellular interaction between these proteins to repress VDR target gene expression, in vivo.
• Hsieh, J., Whitfield, G. K., Jurutka, P. W., Haussler, C. A., Thatcher, M. L., Thompson, P. D., Dang, H. T., Galligan, M. A., Oza, A. K., & Haussler, M. R. (2003). Two basic amino acids C-terminal of the proximal box specify functional binding of the vitamin D receptor to its rat osteocalcin deoxyribonucleic acid-responsive element. Endocrinology, 144(11).
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  Nuclear hormone receptor-responsive element binding specificity has been reported to reside predominantly in the proximal box (P-box), three amino acids located in a DNA-recognition alpha-helix situated on the C-terminal side of the first zinc finger. To further define the residues in the vitamin D receptor (VDR) DNA binding domain (DBD) that mediate its interaction as a retinoid X receptor (RXR) heterodimer with the rat osteocalcin vitamin D-responsive element (VDRE), chimeric receptors were created in which the core DBD of VDR was replaced with that of the homodimerizing glucocorticoid receptor (GR). Systematic alteration of GR DBD amino acids in these chimeras to VDR DBD residues identified arg-49 and lys-53, just C-terminal of the P-box within the base recognition alpha-helix of human VDR (hVDR), as the only two amino acids among 36 differences required to convert the GR core zinc finger domain to that of the VDR. Gel mobility shift and 1,25-dihydroxyvitamin D3-stimulated transcription assays verified that an hVDR-GR DBD chimera is functional on the rat osteocalcin VDRE with only the conservative change of lys-49 to arg, and of the negatively charged glu-53 to a basic amino acid (lys or arg). Thus, for RXR heterodimerizing receptors like VDR, the P-box requires redefinition and expansion to include a DNA specificity element corresponding to arg-49 and lys-53 of hVDR. Examination of DNA specificity element amino acids in other nuclear receptors in terms of conservation and base contact in cocrystal structures supports the conclusion that these residues are crucial for selective DNA recognition.
• Whitfield, G. K., Dang, H. T., Schluter, S. F., Bernstein, R. M., Bunag, T., Manzon, L. A., Hsieh, G., Dominguez, C. E., Youson, J. H., Haussler, M. R., & Marchalonis, J. J. (2003). Cloning of a functional vitamin D receptor from the lamprey (Petromyzon marinus), an ancient vertebrate lacking a calcified skeleton and teeth. Endocrinology, 144(6).
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  The nuclear vitamin D receptor (VDR) mediates the actions of its 1,25-dihydroxyvitamin D(3) ligand to control gene expression in terrestrial vertebrates. Prominent functions of VDR-regulated genes are to promote intestinal absorption of calcium and phosphate for bone mineralization and to potentiate the hair cycle in mammals. We report the cloning of VDR from Petromyzon marinus, an unexpected finding because lampreys lack mineralized tissues and hair. Lamprey VDR (lampVDR) clones were obtained via RT-PCR from larval protospleen tissue and skin and mouth of juveniles. LampVDR expressed in transfected mammalian COS-7 cells bound 1,25-dihydroxyvitamin D(3) with high affinity, and transactivated a reporter gene linked to a vitamin D-responsive element from the human CYP3A4 gene, which encodes a P450 enzyme involved in xenobiotic detoxification. In tests with other vitamin D responsive elements, such as that from the rat osteocalcin gene, lampVDR showed little or no activity. Phylogenetic comparisons with nuclear receptors from other vertebrates revealed that lampVDR is a basal member of the VDR grouping, also closely related to the pregnane X receptors and constitutive androstane receptors. We propose that, in this evolutionarily ancient vertebrate, VDR may function in part, like pregnane X receptors and constitutive androstane receptors, to induce P450 enzymes for xenobiotic detoxification.
• Haussler, M. R., Haussler, C. A., Jurutka, P. W., Encinas Dominguez, C., Hsieh, J. -., Thatcher, M. L., & Whitfield, G. K. (2002). The nuclear vitamin D receptor: from clinical radioreceptor assay of the vitamin D hormone to genomics, proteomics and a novel ligand. J. Clin. Ligand Assay, 221-228.
• Jurutka, P. W., MacDonald, P. N., Nakajima, S., Hsieh, J. -., Thompson, P. D., Whitfield, G. K., Galligan, M. A., Haussler, C. A., & Haussler, M. R. (2002). Isolation of baculovirus-expressed human vitamin D receptor: DNA responsive element interactions and phosphorylation of the purified receptor.. J. Cell. Biochem., 435-457.
• Makishima, M., Lu, T. T., Xie, W., Whitfield, G. K., Domoto, H., Evans, R. M., Haussler, M. R., & Mangelsdorf, D. J. (2002). Vitamin D receptor as an intestinal bile acid sensor. Science (New York, N.Y.), 296(5571).
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  The vitamin D receptor (VDR) mediates the effects of the calcemic hormone 1alpha,25-dihydroxyvitamin D3 [1,25(OH)2D3]. We show that VDR also functions as a receptor for the secondary bile acid lithocholic acid (LCA), which is hepatotoxic and a potential enteric carcinogen. VDR is an order of magnitude more sensitive to LCA and its metabolites than are other nuclear receptors. Activation of VDR by LCA or vitamin D induced expression in vivo of CYP3A, a cytochrome P450 enzyme that detoxifies LCA in the liver and intestine. These studies offer a mechanism that may explain the proposed protective effects of vitamin D and its receptor against colon cancer.
• Thompson, P. D., Jurutka, P. W., Whitfield, G. K., Myskowski, S. M., Eichhorst, K. R., Dominguez, C. E., Haussler, C. A., & Haussler, M. R. (2002). Liganded VDR induces CYP3A4 in small intestinal and colon cancer cells via DR3 and ER6 vitamin D responsive elements. Biochemical and biophysical research communications, 299(5), 730-738.
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  The nuclear vitamin D receptor (VDR) mediates the effects of 1,25-dihydroxyvitamin D(3) (1,25D(3)) to alter intestinal gene transcription and promote calcium absorption. Because 1,25D(3) also exerts anti-cancer effects, we examined the efficacy of 1,25D(3) to induce cytochrome P450 (CYP) enzymes. Exposure of human colorectal adenocarcinoma cells (HT-29) to 10(-8)M 1,25D(3) resulted in >/=3-fold induction of CYP3A4 mRNA and protein as assessed by RT-PCR and Western blotting, respectively. Six vitamin D responsive element (VDRE)-like sequences in the promoter region of the CYP3A4 gene were then individually tested for their ability to enhance transcription. A canonical DR3-type element in the distal region of the promoter (-7719-GGGTCAgcaAGTTCA-7733), and a proximal, non-classical everted repeat with a spacer of 6 bp (ER6; -169-TGAACTcaaaggAGGTCA-152) were identified as functional VDREs in this CYP gene. These data suggest that 1,25D(3)-dependent, VDR-mediated induction of CYP3A4 may constitute a chemoprotective mechanism for detoxification of enteric xenobiotics and carcinogens.
• Jurutka, P. W., Whitfield, G. K., Hsieh, J. -., Thompson, P. D., Haussler, C. A., & Haussler, M. R. (2001). Molecular Nature of the vitamin D receptor and its role in regulation of gene expression.. Reviews in Endocrine & Metabolic Disorders, 203-216.
• Thompson, P. D., Remus, L. S., Hsieh, J. -., Jurutka, P. W., Whitfield, G. K., Galligan, M. A., Encinas Dominguez, C., Haussler, C. A., & Haussler, M. R. (2001). Distinct retinoid X receptor activation function-2 residues mediate transactivation in homodimeric and vitamin D receptor heterodimeric contexts.. J. Mol. Endocrinol., 211-227.
• Whitfield, G. K., Remus, L. S., Jurutka, P. W., Zitzer, H., Oza, A. K., Dang, H. T., Haussler, C. A., Galligan, M. A., Thatcher, M. L., Encinas Dominguez, C., & Haussler, M. R. (2001). Functionally relevant polymorphisms in the human nuclear vitamin D receptor gene.. Mol. Cell. Endocrinol., 145-159.
• Jurutka, P. W., Remus, L. S., Whitfield, G. K., Galligan, M. A., Haussler, C. A., & Haussler, M. R. (2000). Biochemical evidence for a 170 kilodalton, AF-2-dependent vitamin D receptor/retinoid X receptor coactivator that is highly expressed in osteoblasts. Biochem. Biophys. Res. Commun., 813-819.
• Jurutka, P. W., Remus, L. S., Whitfield, G. K., Thompson, P. D., Hsieh, J. -., Zitzer, H., Tavakkoli, P., Galligan, M. A., Dang, H. L., Haussler, C. A., & Haussler, M. R. (2000). The polymorphic N-terminus in human vitamin D receptor isoforms influences transcriptional activity by modulating interaction with transcription factor IIB.. Mol. Endocrinol., 401-420.
• Swamy, N., Xu, W., Paz, N., Hsieh, J. -., Haussler, M. R., Maalouf, G. J., Mohr, S. C., & Ray, R. (2000). Molecular modeling, affinity labeling and site-directed mutagenesis define the key points of interaction between the ligand-binding domain of the vitamin D nuclear receptor and 1alpha,25-dihydroxyvitamin D3.. Biochemistry, 12162-12171.
• Verstuyf, A., Verlinden, L., van Etten, E., Shi, L., Wu, Y., D'Hallleweyn, C., Van Hayer, D., Zhu, G. D., Chen, Y. J., Zhou, X., Haussler, M. R., De Clercq, P., Vandewalle, M., Van Baelen, H., Mathieu, C., & Bouillon, R. (2000). Biological activity of CD-ring modified 1alpha,25-dihydroxyvitamin D analogs: C-ring and five-membered D-ring analogs.. J. Bone Miner. Res., 237-252.