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Endocrine Reviews
Article
Data sources: UnpayWall
image/svg+xml art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos Open Access logo, converted into svg, designed by PLoS. This version with transparent background. http://commons.wikimedia.org/wiki/File:Open_Access_logo_PLoS_white.svg art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos http://www.plos.org/
image/svg+xml art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos Open Access logo, converted into svg, designed by PLoS. This version with transparent background. http://commons.wikimedia.org/wiki/File:Open_Access_logo_PLoS_white.svg art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos http://www.plos.org/
Endocrine Reviews
Article . 2010 . Peer-reviewed
Data sources: Crossref
The Journal of Clinical Endocrinology & Metabolism
Article . 2010 . Peer-reviewed
Data sources: Crossref
Molecular Endocrinology
Article . 2010 . Peer-reviewed
Data sources: Crossref
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A Novel Bile Acid-Activated Vitamin D Receptor Signaling in Human Hepatocytes

Authors: Shuxin, Han; Tiangang, Li; Ewa, Ellis; Stephen, Strom; John Y L, Chiang;

A Novel Bile Acid-Activated Vitamin D Receptor Signaling in Human Hepatocytes

Abstract

ABSTRACT Vitamin D receptor (VDR) is activated by natural ligands, 1α, 25-dihydroxy-vitamin D3 (1α, 25(OH)2-D3) and lithocholic acid (LCA). Our previous study shows that VDR is expressed in human hepatocytes, and VDR ligands inhibit bile acid synthesis and transcription of the gene encoding cholesterol 7α-hydroxylase (CYP7A1). Primary human hepatocytes were used to study LCA and 1α, 25(OH)2-D3 activation of VDR signaling. Confocal immunofluorescent microscopy imaging and immunoblot analysis showed that LCA and 1α, 25(OH)2-D3 induced intracellular translocation of VDR from the cytosol to the nucleus, and also plasma membrane where VDR co-localized with caveolin-1. VDR ligands induced tyrosine phosphorylation of c-Src and VDR, and their interaction. Inhibition of c-Src abrogated VDR ligand-dependent inhibition of CYP7A1 mRNA expression. Kinase assays showed that VDR ligands specifically activated the c-Raf/MEK1/2/ERK1/2 pathway, which stimulates serine phosphorylation of VDR and HNF4α, and their interaction. Mammalian two-hybrid assays showed a VDR ligand dependent interaction of nuclear receptor corepressor-1 (NCoR-1) and silencing mediator of retinoid and thyroid (SMRT) with VDR/RXRα. Chromatin immunoprecipitation assays revealed that an ERK1/2 inhibitor reversed VDR ligand-induced recruitment of VDR, RXRα and corepressors to human CYP7A1 promoter. In conclusion, VDR ligands activate membrane VDR signaling to activate the MEK1/2/ERK1/2 pathway, which stimulates nuclear VDR/RXRα recruitment of co-repressors to inhibit CYP7A1 gene transcription in human hepatocytes. This membrane VDR signaling pathway may be activated by bile acids to inhibit bile acid synthesis as a rapid response to protect hepatocytes from cholestatic liver injury.

Keywords

Cell Nucleus, Mitogen-Activated Protein Kinase Kinases, Cell Membrane, Intracellular Space, Hep G2 Cells, Ligands, Enzyme Activation, Proto-Oncogene Proteins c-raf, Protein Transport, Calcitriol, Hepatocyte Nuclear Factor 4, Hepatocytes, Humans, Lithocholic Acid, Phosphorylation, Cholesterol 7-alpha-Hydroxylase, Extracellular Signal-Regulated MAP Kinases, Phosphotyrosine, Promoter Regions, Genetic, Protein Kinase Inhibitors

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    This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
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    This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
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citations
This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Citations provided by BIP!
popularity
This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
BIP!Popularity provided by BIP!
influence
This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Influence provided by BIP!
impulse
This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
BIP!Impulse provided by BIP!
122
Top 10%
Top 10%
Top 1%
bronze