Vitamin D Receptor Expression in Chicken Muscle Tissue and Cultured Myoblasts

Sb, Zanello; Ed, Collins; Mj, Marinissen; Aw, Norman; Rl, Boland

doi:10.1055/s-2007-979027

Cited by 51 publications

(23 citation statements)

References 12 publications

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“…The activation process of the glucocorticoid receptor (GR), androgen receptor, and progesterone receptor also includes a translocation of these receptors from the cytoplasm to the nucleus. For many years, however, VDR has been considered to reside exclusively in the nucleus even without hormone (8,9). More recently, significant amounts of unliganded VDR was found in the cytoplasm with immunocytology (10,11) and with fluorescent labeled hormone in living cells (12).…”

Section: The Vitamin D Receptor (Vdr)mentioning

confidence: 99%

Hormone-dependent Translocation of Vitamin D Receptors Is Linked to Transactivation

Rácz

Bársony

1999

Journal of Biological Chemistry

104

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Vitamin D receptor (VDR) acts as a transcription factor mediating genomic actions of calcitriol. Our earlier studies suggested that calcitriol induces translocation of cytoplasmic VDR, but the physiologic relevance of this finding remained uncertain. Previous studies demonstrated that the activation function 2 domain (AF-2) plays an essential role in VDR transactivation. To elucidate hormone-dependent VDR translocation and its role, we constructed green fluorescent protein (GFP) chimeras with full-length VDR (VDR-GFP), AF-2-truncated VDR (AF-2del-VDR-GFP), and ligand-binding domain (LBD)-truncated VDR (LBDdel-VDR-GFP). COS-7 cells were transiently transfected with these constructs. Western blot analysis, fluorescent microscopy, and transactivation assays showed that the generated chimeras are expressed and fluoresce and that VDR-GFP is transcriptionally active. After hormone treatment, cytoplasmic VDR-GFP translocated to the nucleus in a concentration-, time-, temperature-, and analog-specific manner. Hormone dose-response relationships for translocation and for transactivation were similar. Truncation of LBD and truncation of AF-2 each abolished hormone-dependent translocation and transactivation. Our data confirm a hormone-dependent VDR translocation, demonstrate that an intact AF-2 domain is required for this translocation, and indicate that translocation is part of the receptor activation process. The vitamin D receptor (VDR)1 is a member of the steroid/ thyroid superfamily of transcription factors that mediates gene expression in a calcitriol-dependent fashion. The hormonally active form of vitamin D, calcitriol, is the principal regulator of calcium homeostasis and also regulates hormone secretion, immune functions, cell proliferation, and differentiation (1). After ligand binding, VDR undergoes an activation process. The mechanism and the regulatory steps involved in this activation process are under intense investigation. An understanding of these activation steps offers possibilities for selective pharmacological modulation of steroid hormone actions.Recent studies showed that steroid receptor activation involves conformational changes (2, 3), phosphorylation/dephosphorylation (4), interactions with coregulator proteins (2, 5, 6), and dimerization (7). The activation process of the glucocorticoid receptor (GR), androgen receptor, and progesterone receptor also includes a translocation of these receptors from the cytoplasm to the nucleus. For many years, however, VDR has been considered to reside exclusively in the nucleus even without hormone (8, 9). More recently, significant amounts of unliganded VDR was found in the cytoplasm with immunocytology (10, 11) and with fluorescent labeled hormone in living cells (12). These studies also showed a shift from cytoplasm into the nucleus after calcitriol exposure. Nevertheless, subcellular distribution of VDR remained controversial. Dynamic studies were needed in living cells to clarify the intracellular localization of VDR and to investigate the physiologic si...

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Section: The Vitamin D Receptor (Vdr)mentioning

confidence: 99%

Hormone-dependent Translocation of Vitamin D Receptors Is Linked to Transactivation

Rácz

Bársony

1999

Journal of Biological Chemistry

104

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“…Early clinical descriptions of a reversible myopathy associated with vitamin D deficiency and/or chronic renal failure recognized a potential association between vitamin D and muscle (Boland, 1986). The identification of the vitamin D receptor (VDR) on muscle cells (Zanello et al, 1997;Bischoff et al, 2001) provided further support for a direct effect of vitamin D on muscle tissue. Recent investigations in cell culture and animals have advanced our understanding of some of the molecular mechanisms through which vitamin D targets skeletal muscle; however, much remains to be characterized.…”

Section: Introductionmentioning

confidence: 99%

Vitamin D and skeletal muscle tissue and function

Ceglia

2008

Molecular Aspects of Medicine

300

219

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“…These experiments also revealed that the apparent nuclear/cytosol distribution depends upon the ionic strength of the extraction buffer used in the subcellular fractionation procedure [Walters et al, 1980]. Nevertheless, immunocytochemical localization studies confirm that, in situ, VDR is primarily a nuclear protein even in the ligand unoccupied state [Berger et al, 1988;Clemens et al, 1988;Milde et al, 1989;Zanello et al, 1997] .…”

mentioning

confidence: 99%

Novel nuclear localization signal between the two DNA-binding zinc fingers in the human vitamin D receptor

et al. 1998

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The human vitamin D receptor (hVDR) possesses a unique array of five basic amino acids positioned between the two DNA-binding zinc fingers that is similar to well-characterized nuclear localization sequences in other proteins. When residues within this region are mutated to nonbasic amino acids, or when this domain is deleted, the receptor is still well expressed, but it no longer associates with the vitamin D-responsive element in DNA, in vitro, and hVDR-mediated transcriptional activation is abolished in transfected cells. Concomitantly, the mutated hVDRs exhibit a significant shift in hVDR cellular distribution favoring cytoplasmic over nuclear retention as assessed by subcellular fractionation and immunoblotting. Independent immunocytochemical studies employing a VDR-specific monoclonal antibody demonstrate that mutation or deletion of this basic domain dramatically attenuates hVDR nuclear localization in transfected COS-7 cells. Although wild-type hVDR is partitioned predominantly to the nucleus in the absence of the 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) hormone, treatment with ligand further enhances nuclear translocation, as it does to some degree in receptors with the basic region altered. The role of 1,25(OH)2D3 may be to facilitate hVDR heterodimerization with retinoid X receptors, stimulating subsequent DNA binding and ultimately enhancing nuclear retention. Taken together, these data reveal that the region of hVDR between Arg-49 and Lys-55 contains a novel constitutive nuclear localization signal, RRSMKRK.

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Vitamin D Receptor Expression in Chicken Muscle Tissue and Cultured Myoblasts

Cited by 51 publications

References 12 publications

Hormone-dependent Translocation of Vitamin D Receptors Is Linked to Transactivation

Hormone-dependent Translocation of Vitamin D Receptors Is Linked to Transactivation

Vitamin D and skeletal muscle tissue and function

Novel nuclear localization signal between the two DNA-binding zinc fingers in the human vitamin D receptor

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