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TGR5 in the Biliary Tree

TGR5 in the Biliary Tree

Verena Keitel, Dieter Häussinger

Dig Dis. 2011;29(1):45-7.

PMID: 21691103

Abstract:

Background/aims:
TGR5 is a plasma membrane-bound, G-protein-coupled receptor for bile acids. TGR5 mRNA has been detected in a variety of tissues, including liver. The aim of the present study was to determine the localization and function of the receptor in biliary epithelial cells.
Methods:
Liver and gallbladder tissue from humans and rodents were analyzed for TGR5 expression and localization by real-time PCR, Western blot and immunofluorescence microscopy. Cholangiocytes and gallbladder epithelial cells were isolated from wild-type and TGR5 knockout mice. Cyclic AMP (cAMP) was measured using a radioimmunoassay and chloride concentrations were analyzed using the chloride-sensitive dye N-(ethoxycarbonylmethyl)-6-methoxyquinolinium bromide (MQAE). Cell proliferation was determined by bromodeoxyuridine incorporation.
Results:
TGR5 is localized in the apical membrane and the primary cilium of cholangiocytes and gallbladder epithelial cells. Activation of the receptor by bile acids led to a rise in intracellular cAMP concentrations and a decrease in intracellular chloride concentrations as measured by MQAE fluorescence, indicating increased chloride secretion. This effect could be abolished in the presence of an inhibitor of the cAMP-dependent chloride channel cystic fibrosis transmembrane conductance regulator. Furthermore, activation of TGR5 by bile acids induced cholangiocyte proliferation, which was not observed in cells derived from TGR5 knockout mice.
Conclusion:
In biliary epithelial cells, TGR5 acts as a bile acid sensor coupling biliary bile acid concentrations to bile formation. Furthermore, the receptor may play a role in bile acid-dependent cholangiocyte proliferation and may protect biliary epithelial cells from bile acid-induced cell death.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP162558523	1-(Ethoxycarbonylmethyl)-6-methoxyquinolinium bromide		162558-52-3	Price

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