Organic solute transporter subunit beta (SLC51B)

Organic solute transporter subunit beta (SLC51B) is a single-pass transmembrane protein that partners with SLC51A (OSTα) to form the OSTα-OSTβ heterodimer. This transporter is essential for the basolateral export of bile acids, conjugated steroids, and prostaglandin E2 from epithelial cells, especially in the small intestine, liver, kidney, and other tissues involved in steroid and bile acid circulation. The SLC51A/SLC51B complex is required for normal bile acid absorption and dietary lipid uptake, acts independently of sodium, and is subject to adaptive transcriptional regulation in response to changes in bile acid load, often mediated via the FXR nuclear receptor. Mutations or absence of transporter function lead to profound alterations in bile acid and lipid metabolism. OSTβ is necessary for glycosylation and membrane targeting of OSTα, and both subunits must heterodimerize for stability and trafficking. Several clinically used drugs are known to inhibit OSTα/OSTβ-mediated transport. Increased expression of this transporter is found in cholestatic liver disease, supporting its role in hepatic bile acid adaptation and protection against toxicity.

Other names

OST-betaOSTBOSTBETASolute carrier family 51 subunit betaSLC51A1 binding proteinSLC51A1BPPBAM2Organic solute transporter beta subunit

Inhibition of bile acid and steroid conjugate efflux or uptake (by competitive blockade of the transporter); Modulation of intestinal/liver/kidney bile acid homeostasis; FXR-dependent transcriptional regulation alters transporter expression and function