Review article: The function and regulation of proteins involved in bile salt biosynthesis and transport.
BACKGROUND
Bile salts are produced and secreted by the liver and are required for intestinal absorption of fatty food components and excretion of endobiotics and xenobiotics. They are reabsorbed in the terminal ileum and transported back to the liver via the portal tract. Dedicated bile salt transporters in hepatocytes and enterocytes are responsible for the unidirectional transport of bile salts in the enterohepatic cycle.


OBJECTIVE
To give an overview of the function and regulations of proteins involved in bile salt synthesis and transport.


METHODS
Data presented are obtained from PubMed-accessible literature combined with our own recent research.


RESULTS
Hepatocytes and enterocytes contain unique bile salt importers (sodium-taurocholate cotransporting polypeptide and apical sodium-dependent bile acid transporter, respectively) and exporters (bile salt export pump and organic solute transporter alpha-beta, respectively). Enzymes involved in bile salt biosynthesis reside in different subcellular locations, including the endoplasmic reticulum, mitochondria, cytosol and peroxisomes. Defective expression or function of the transporters or enzymes may lead to cholastasis. The bile salt-activated transcription factor Farnesoid X receptor controls expression of genes involved in bile salt biosynthesis and transport.


CONCLUSIONS
Detailed knowledge is available about the enzymes and transporters involved in bile salt homeostasis and how their defective function is associated with cholestasis. In contrast, the process of intracellular bile salt transport is largely unexplored.
Pellicoro
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A
Department of Gastroenterology and Hepatology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
Faber
K N
KN
D001647:Bile Acids and Salts / Q000096:biosynthesis / Q000378:metabolism*; D001692:Biological Transport; D002352:Carrier Proteins / Q000378:metabolism*; D002779:Cholestasis / Q000378:metabolism*; D004764:Enterohepatic Circulation / Q000502:physiology; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D029363:Organic Anion Transporters, Sodium-Dependent / Q000096:biosynthesis / Q000378:metabolism*; D027981:Symporters / Q000096:biosynthesis / Q000378:metabolism*
D001647:Bile Acids and Salts; D002352:Carrier Proteins; D029363:Organic Anion Transporters, Sodium-Dependent; D027981:Symporters; C071908:sodium-bile acid cotransporter