1
40
5
-
Text
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URL Address
<a href="http://doi.org/10.1152/ajpgi.00170.2004" target="_blank" rel="noreferrer noopener">http://doi.org/10.1152/ajpgi.00170.2004</a>
Rights
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
Pages
G60-G66
Issue
1
Volume
288
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Dublin Core
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Title
A name given to the resource
Fxr-activating Ligands Inhibit Rabbit Asbt Expression Via Fxr-shp-ftf Cascade
Publisher
An entity responsible for making the resource available
American Journal of Physiology-Gastrointestinal and Liver Physiology
Date
A point or period of time associated with an event in the lifecycle of the resource
2005
2005-01
Subject
The topic of the resource
bile-acid transporter; cloning; down-regulation; Gastroenterology & Hepatology; identification; ileal; messenger-rna; negative feedback-regulation; nuclear receptor; Physiology; rats; real-time
Creator
An entity primarily responsible for making the resource
Li H; Chen F; Shang Q; Pan L X; Shneider B L; Chiang J Y L; Forman B M; Ananthanarayanan M; Tint G S; Salen G; Xu G R
Description
An account of the resource
The regulation of the rabbit apical sodium-dependent bile acid transporter ( ASBT) was studied both in vivo and in vitro. New Zealand White rabbits were fed 0.5% deoxycholic acid (DCA) or SC-435, a competitive ASBT inhibitor, for 1 wk. In DCA-fed rabbits, ASBT expression was repressed, associated with activated FXR, and evidenced by increased ileal short heterodimer partner (SHP) mRNA. Feeding SC-435 to the rabbits blocked bile acid absorption, decreased SHP mRNA, and increased ASBT expression. A 1.9-kb rabbit ASBT 5'-flanking region (promoter) was cloned, and a cis-acting element for alpha-fetoprotein transcription factor (FTF) was identified (-1166/-1158). The effects of transcriptional factors and different bile acids on the rabbit ASBT promoter were studied in Caco-2 cells. FTF stimulated the rabbit ASBT promoter activity fourfold but not after the FTF binding site was deleted from the promoter. Increasing the SHP protein notably inhibited FTF-dependent trans-activation of rabbit ASBT. Adding hydrophobic bile acids deoxycholic acid, chenodeoxycholic acid, and cholic acid, activating ligands for FXR, inhibited rabbit ASBT promoter activity in Caco-2 cells, but this inhibitory effect was abolished after the FTF binding site was deleted. Ursodeoxycholic acid and ursocholic acid, nonactivating ligands for FXR, did not repress ASBT promoter activity. Thus the rabbit ASBT promoter is negative-feedback regulated by bile acids via a functional FTF binding site. Only FXR-activating ligands can downregulate rabbit ASBT expression through the regulatory cascade FXR-SHP-FTF.
Identifier
An unambiguous reference to the resource within a given context
<a href="http://doi.org/10.1152/ajpgi.00170.2004" target="_blank" rel="noreferrer noopener">10.1152/ajpgi.00170.2004</a>
Format
The file format, physical medium, or dimensions of the resource
Journal Article or Conference Abstract Publication
2005
American Journal of Physiology-Gastrointestinal and Liver Physiology
Ananthanarayanan M
bile-acid transporter
Chen F
Chiang J Y L
Cloning
Down-Regulation
Forman B M
Gastroenterology & Hepatology
identification
ileal
Journal Article or Conference Abstract Publication
Li H
messenger-rna
negative feedback-regulation
Nuclear Receptor
Pan L X
Physiology
Rats
real-time
Salen G
Shang Q
Shneider B L
Tint G S
Xu G R
-
Text
A resource consisting primarily of words for reading. Examples include books, letters, dissertations, poems, newspapers, articles, archives of mailing lists. Note that facsimiles or images of texts are still of the genre Text.
URL Address
<a href="http://doi.org/10.1016/s0016-5085(01)80063-9" target="_blank" rel="noreferrer noopener">http://doi.org/10.1016/s0016-5085(01)80063-9</a>
Rights
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
Pages
A13-A13
Issue
5
Volume
120
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Dublin Core
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Title
A name given to the resource
CYP7A1 is inhibited by activated FXR via SHP and LRH-1 in cholesterol-fed rabbits
Publisher
An entity responsible for making the resource available
Gastroenterology
Date
A point or period of time associated with an event in the lifecycle of the resource
2001
2001-04
Subject
The topic of the resource
Gastroenterology & Hepatology
Creator
An entity primarily responsible for making the resource
Xu G R; Ananthanarayanan M; Forman B M; Li X G; Shefer S; Erickson S; Chiang J Y L; Tint G S; Salen G
Identifier
An unambiguous reference to the resource within a given context
<a href="http://doi.org/10.1016/s0016-5085(01)80063-9" target="_blank" rel="noreferrer noopener">10.1016/s0016-5085(01)80063-9</a>
Format
The file format, physical medium, or dimensions of the resource
Journal Article
2001
Ananthanarayanan M
Chiang J Y L
Erickson S
Forman B M
Gastroenterology
Gastroenterology & Hepatology
Journal Article
Li X G
Salen G
Shefer S
Tint G S
Xu G R
-
Text
A resource consisting primarily of words for reading. Examples include books, letters, dissertations, poems, newspapers, articles, archives of mailing lists. Note that facsimiles or images of texts are still of the genre Text.
URL Address
<a href="http://doi.org/10.1194/jlr.M500449-JLR200" target="_blank" rel="noreferrer noopener">http://doi.org/10.1194/jlr.M500449-JLR200</a>
Rights
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
Pages
997-1004
Issue
5
Volume
47
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Title
A name given to the resource
The stimulatory effect of LXR alpha is blocked by SHP despite the presence of a LXR alpha binding site in the rabbit CYP7A1 promoter
Publisher
An entity responsible for making the resource available
Journal of Lipid Research
Date
A point or period of time associated with an event in the lifecycle of the resource
2006
2006-05
Subject
The topic of the resource
alpha-fetoprotein transcription; bile-acid biosynthesis; Biochemistry & Molecular Biology; cholesterol 7 alpha-hydroxylase; cholesterol 7-alpha-hydroxylase gene; dietary-cholesterol; dietary-cholesterol; factor; farnesoid X receptor; farnesoid X receptor; inhibition; liver X receptor; messenger-rna levels; nuclear receptor; orphan; rat; SHP; taurocholate; transcription
Creator
An entity primarily responsible for making the resource
Shang Q; Pan L X; Saumoy M; Chiang J Y L; Tint G S; Salen G; Xu G R
Description
An account of the resource
The transcription of the cholesterol 7 alpha-hydroxylase gene (CYP7A1) is greatly decreased in cholesterol-fed rabbits. To determine whether the molecular structure of the promoter is responsible for this downregulation, we cloned the rabbit CYP7A1 promoter, identified the binding sites for a-fetoprotein transcription factor (FTF) and liver X receptor (LXR alpha), and studied the effects of FTF, LXR alpha, and SHP on its transcription. Adding LXR alpha/retinoid X receptor together with their ligands (L/R) to the promoter/reporter construct transfected into HepG2 cells greatly increased its activity. FTF did not increase promoter activity, nor did it enhance the stimulatory effect of L/R. Mutating the FTF binding site abolished the promoter baseline activity. Increasing amounts of SHP abolished the effect of L/R, and FTF enhanced the ability of SHP to decrease promoter activity below baseline levels. Thus, downregulation of CYP7A1 in cholesterol-fed rabbits is attributable secondarily to the activation of farnesoid X receptor, which increases SHP expression to override the positive effects of LXR alpha. Although FFF is a competent factor for maintaining baseline activity, it does not further enhance and may suppress CYP7A1 transcription.
Identifier
An unambiguous reference to the resource within a given context
<a href="http://doi.org/10.1194/jlr.M500449-JLR200" target="_blank" rel="noreferrer noopener">10.1194/jlr.M500449-JLR200</a>
Format
The file format, physical medium, or dimensions of the resource
Journal Article
2006
alpha-fetoprotein transcription
bile-acid biosynthesis
Biochemistry & Molecular Biology
Chiang J Y L
cholesterol 7 alpha-hydroxylase
cholesterol 7-alpha-hydroxylase gene
dietary-cholesterol
factor
Farnesoid X receptor
inhibition
Journal Article
Journal of lipid research
liver X receptor
messenger-rna levels
Nuclear Receptor
orphan
Pan L X
rat
Salen G
Saumoy M
Shang Q
SHP
taurocholate
Tint G S
Transcription
Xu G R
-
Text
A resource consisting primarily of words for reading. Examples include books, letters, dissertations, poems, newspapers, articles, archives of mailing lists. Note that facsimiles or images of texts are still of the genre Text.
URL Address
<a href="http://doi.org/10.1152/ajpgi.00209.2007" target="_blank" rel="noreferrer noopener">http://doi.org/10.1152/ajpgi.00209.2007</a>
Rights
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
Pages
G817-G823
Issue
4
Volume
293
Search for Full-text
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Title
A name given to the resource
An overlapping binding site in the CYP7A1 promoter allows activation of FXR to override the stimulation by LXR alpha
Publisher
An entity responsible for making the resource available
American Journal of Physiology-Gastrointestinal and Liver Physiology
Date
A point or period of time associated with an event in the lifecycle of the resource
2007
2007-10
Subject
The topic of the resource
7-alpha-hydroxylase gene; activity; bile-acid biosynthesis; cholesterol; cholesterol 7 alpha-hydroxylase; dietary-cholesterol; down-regulation; farnesoid X; fetoprotein transcription factor; Gastroenterology & Hepatology; heterodimer partner; liver X receptor; LXR binding site; messenger-rna; metabolism; orphan nuclear receptor; Physiology; rat; receptor; regulation; short; transcriptional; x-receptor
Creator
An entity primarily responsible for making the resource
Shang Q; Pan L X; Saumoy M; Chiang J Y L; Tint G S; Salen G; Xu G R
Description
An account of the resource
An overlapping binding site in the CYP7A1 promoter allows activation of FXR to override the stimulation by LXR alpha. Am J Physiol Gastrointest Liver Physiol 293: G817-G823, 2007. First published August 9, 2007; doi:10.1152/ajpgi.00209.2007.-The aim of this study was to explore why in rabbits activation of farnesoid X receptor (FXR) is dominant over activated liver X receptor-alpha (LXR alpha) in the regulation of CYP7A1. We cloned the rabbit CYP7A1 promoter and found a fetoprotein transcription factor (FTF) binding element embedded within the LXR alpha binding site (LXRE). Gel shift assays demonstrated that FTF competes with LXR alpha for binding to LXRE. Short heterodimer partner (SHP) enhances the competitive ability of FTF. Studies in HepG2 cells showed that SHP combined with FTF had more powerful effect to offset the stimulation of CYP7A1 by LXR alpha. Gel shift and chromatin immunoprecipitation assays demonstrated that SHP with FTF diminished LXR alpha\binding to the CYP7A1 promoter. In vivo studies in rabbits fed cholesterol for 10 days showed that hepatic expression of SHP but not FTF rose and LXR alpha-bound LXRE decreased. We propose that the SHP/FTF heterodimer occupies LXRE via the embedded FTF binding element and blocks LXR alpha from recruiting to LXRE. Therefore, activation of FXR, which upregulates SHP expression, will eliminate the stimulatory effect of LXR alpha on the CYP7A1 promoter because increased levels of SHP combined with FTF diminish the recruitment of LXR alpha to CYP7A1 promoter.
Identifier
An unambiguous reference to the resource within a given context
<a href="http://doi.org/10.1152/ajpgi.00209.2007" target="_blank" rel="noreferrer noopener">10.1152/ajpgi.00209.2007</a>
Format
The file format, physical medium, or dimensions of the resource
Journal Article
2007
7-alpha-hydroxylase gene
activity
American Journal of Physiology-Gastrointestinal and Liver Physiology
bile-acid biosynthesis
Chiang J Y L
Cholesterol
cholesterol 7 alpha-hydroxylase
dietary-cholesterol
Down-Regulation
farnesoid X
fetoprotein transcription factor
Gastroenterology & Hepatology
heterodimer partner
Journal Article
liver X receptor
LXR binding site
messenger-rna
Metabolism
orphan nuclear receptor
Pan L X
Physiology
rat
Receptor
regulation
Salen G
Saumoy M
Shang Q
short
Tint G S
transcriptional
x-receptor
Xu G R
-
Text
A resource consisting primarily of words for reading. Examples include books, letters, dissertations, poems, newspapers, articles, archives of mailing lists. Note that facsimiles or images of texts are still of the genre Text.
URL Address
<a href="http://doi.org/10.1053/jhep.1996.v24.pm0008938182" target="_blank" rel="noreferrer noopener">http://doi.org/10.1053/jhep.1996.v24.pm0008938182</a>
Rights
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
Pages
1468-1474
Issue
6
Volume
24
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Title
A name given to the resource
Cholesterol 7 alpha-hydroxylase activities from human and rat liver are modulated in vitro posttranslationally by phosphorylation/dephosphorylation
Publisher
An entity responsible for making the resource available
Hepatology
Date
A point or period of time associated with an event in the lifecycle of the resource
1996
1996-12
Subject
The topic of the resource
bile-acid synthesis; cloning; dietary-cholesterol; enzyme; Escherichia coli; expression; Gastroenterology & Hepatology; hmg-coa reductase; messenger-rna levels; Phosphatase; purification
Creator
An entity primarily responsible for making the resource
Nguyen L B; Shefer S; Salen G; Chiang J Y L; Patel M
Description
An account of the resource
Purified cholesterol 7 alpha-hydroxylases (C7 alpha H) from human and rat liver microsomes, and from transformed Escherichia coli expression systems, were incubated with 0.3 mmol/L [gamma-P-32] adenosine triphosphate (ATP) in the presence and absence of bacterial alkaline phosphatase (AP) or rabbit muscle adenosine 3',5'-cyclic monophosphate (cAMP) dependent protein kinase. The amounts of P-32 incorporation after separation of human and rat C7 alpha H proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) were related to C7 alpha H catalytic activities (determined by a radioisotope incorporation method) and enzyme protein mass (determined by Western blotting and laser densitometry). Both human and rat C7 alpha H activities significantly decreased after dephosphorylation by AP (-57%--72%) and increased up to twofold with phosphorylation by rabbit muscle cAMP-dependent protein kinase. The increases in C7 alpha H activities were proportional to the amounts of cAMP-dependent protein kinase used, and were coupled to P-32 incorporation into the purified enzymes, Both the activation of C7 alpha H and the amounts of P-32 incorporation were time-dependent and reached a maximum after 1 hour of incubation with 5 U of cAMP-dependent protein kinase. In a second set of experiments, purified human and rat Liver C7 alpha H were dephosphorylated by 30-minute incubation with AP, followed by inactivation of the phosphatase by the inhibitor NaF, and rephosphorylation of C7 alpha H by 30-minute incubation with rabbit muscle cAMP-dependent protein kinase or bovine heart cAMP-independent protein kinase. Rephosphorylation of the dephosphorylated C7 alpha H proteins by cAMP-dependent protein kinase increased C7 alpha H catalytic activities up to fourfold, and the stimulation in catalytic activities paralleled the increases in P-32 incorporation into the purified enzymes. Bovine heart protein kinase was as potent as rabbit muscle cAMP-dependent protein kinase in stimulating catalytic activity and P-32 incorporation into the human C7 alpha H protein. Because the protein mass of these purified enzymes did not change, the short-term regulation or catalytic efficiency of C7 alpha H (activity per protein mass unit) is modulated, in vitro, posttranslationally by a phosphorylation/ dephosphorylation mechanism in both the human and the rat enzymes.
Identifier
An unambiguous reference to the resource within a given context
<a href="http://doi.org/10.1053/jhep.1996.v24.pm0008938182" target="_blank" rel="noreferrer noopener">10.1053/jhep.1996.v24.pm0008938182</a>
Format
The file format, physical medium, or dimensions of the resource
Journal Article
1996
bile-acid synthesis
Chiang J Y L
Cloning
Department of Internal Medicine
dietary-cholesterol
enzyme
Escherichia coli
expression
Gastroenterology & Hepatology
Hepatology
HMG-CoA reductase
Journal Article
messenger-rna levels
NEOMED College of Medicine
Nguyen L B
Patel M
Phosphatase
purification
Salen G
Shefer S