Farsenoid X receptor



The bile acid receptor also known as farnesoid X receptor (FXR) or NR1H4 is a nuclear receptor that is encoded by the NR1H4 gene.


The  NR1H4 gene is located on Chromosome 12.


FXR is expressed at high levels in the liver and intestine. 


Chenodeoxycholic acid and other bile acids are natural ligands for FXR. 


FXR translocates to the cell nucleus, forms a dimer and binds to hormone response elements on DNA, which up- or down-regulates the expression of certain genes.


A primary function,of FXR activation is the suppression of cholesterol 7 alpha-hydroxylase (CYP7A1), the rate-limiting enzyme in bile acid synthesis from cholesterol. 


FXR induces expression,functions to inhibit transcription of the CYP7A1 gene as a negative feedback pathway is established in which synthesis of bile acids is inhibited when cellular levels are already high.


FXR is important in regulation of hepatic triglyceride levels.


FXR activation suppresses lipogenesis and promotes free fatty acid oxidation by  peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PPARĪ±) activation.


FXR regulates the expression and activity of epithelial transport proteins involved in fluid homeostasis in the intestine (cystic fibrosis transmembrane conductance regulator (CFTR).


Farnesoid X receptor has been shown to interact with:


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