Intracellular transport of bile acids.
Bile acids originate from the liver and are transported via bile to the intestines where they perform an important role in the absorption of lipids and lipid-soluble nutrients. Most of the bile acids are reclaimed from the terminal ileum and returned to the liver via portal blood for reuse. The transport of bile acids is vectorial in both liver and intestinal cells, originating and terminating at opposite poles. Bile acids enter through the basolateral pole in liver cells, and through the apical pole in intestinal cells. During the past decade, much has been learned about the mechanisms by which bile acids enter and exit liver and intestinal cells. By contrast, the mechanisms by which bile acids are transported across cells remain poorly understood. The current body of evidence suggests that bile acids do not traverse the cell by vesicular transport. Although a carrier-mediated mechanism is a likely alternative, only a handful of intracellular proteins capable of binding bile acids have been described. The significance of these proteins in the intracellular transport of bile acids remains to be tested.
Agellon
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Department of Biochemistry, University of Alberta, Edmonton, Alta, Canada. luis.agellon@ualberta.ca
Torchia
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D000818:Animals; D027321:Anion Transport Proteins; D001647:Bile Acids and Salts / Q000096:biosynthesis / Q000097:blood / Q000378:metabolism*; D001648:Bile Canaliculi / Q000378:metabolism; D001692:Biological Transport; D002352:Carrier Proteins / Q000378:metabolism; D053493:Cholestanetriol 26-Monooxygenase; D002790:Cholesterol 7-alpha-Hydroxylase / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D020895:Enterocytes / Q000378:metabolism; D006801:Humans; D007082:Ileum / Q000378:metabolism; D008099:Liver / Q000378:metabolism*; D013250:Steroid Hydroxylases / Q000378:metabolism; D013656:Taurocholic Acid / Q000378:metabolism; D014407:Tumor Cells, Cultured
D027321:Anion Transport Proteins; D001647:Bile Acids and Salts; D002352:Carrier Proteins; D013656:Taurocholic Acid; D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases; D002790:Cholesterol 7-alpha-Hydroxylase; C506831:CYP27A1 protein, human; D053493:Cholestanetriol 26-Monooxygenase