OST alpha-OST beta: a key membrane transporter of bile acids and conjugated steroids

Front Biosci (Landmark Ed). 2009 Jan 1;14(8):2829-44. doi: 10.2741/3416.


The organic solute and steroid transporter, Ost alpha-Ost beta, is an unusual heteromeric carrier that appears to play a central role in the transport of bile acids, conjugated steroids, and structurally-related molecules across the basolateral membrane of many epithelial cells. The transporter's substrate specificity, transport mechanism, tissue distribution, subcellular localization, transcriptional regulation, as well as the phenotype of the recently characterized Ost alpha-deficient mice all strongly support this model. In particular, the Ost alpha-deficient mice display a marked defect in intestinal bile acid and conjugated steroid absorption; a decrease in bile acid pool size and serum bile acid levels; altered intestinal, hepatic and renal disposition of known substrates of the transporter; and altered serum triglyceride, cholesterol, and glucose levels. Collectively, the data indicate that Ost alpha-Ost beta is essential for bile acid and sterol disposition, and suggest that the carrier may be involved in human conditions related to imbalances in bile acid or lipid homeostasis.

Publication types

  • Research Support, N.I.H., Extramural
  • Review

MeSH terms

  • Bile Acids and Salts / biosynthesis
  • Bile Acids and Salts / metabolism*
  • Biological Transport
  • Dimerization
  • Humans
  • Intestinal Mucosa / metabolism
  • Liver / metabolism
  • Membrane Transport Proteins / chemistry
  • Membrane Transport Proteins / metabolism
  • Membrane Transport Proteins / physiology*
  • Steroids / metabolism*


  • Bile Acids and Salts
  • Membrane Transport Proteins
  • Steroids