High impact information on OSTbeta

• Transport in OSTalpha-OSTbeta-expressing Xenopus laevis oocytes was unaffected by depletion of intracellular adenosine triphosphate, or by changes in transmembrane Na(+), K(+), H(+), or Cl(-) concentration gradients [1].
• Indirect immunofluorescence microscopy localized OSTalpha and OSTbeta to the basolateral membrane of mouse, rat, and human ileal enterocytes, renal proximal tubular cells, and cholangiocytes [1].
• OSTalpha-OSTbeta: a major basolateral bile acid and steroid transporter in human intestinal, renal, and biliary epithelia [1].
• Human and mouse OSTalpha-OSTbeta also were able to mediate transport of taurocholate, digoxin, and prostaglandin E2 but not of estradiol 17beta-d-glucuronide or p-aminohippurate [2].
• OSTalpha and OSTbeta were able to reach the oocyte plasma membrane when expressed either individually or in pairs, indicating that co-expression is not required for proper membrane targeting [2].

Biological context of OSTbeta

• In contrast to all other organic anion transporters identified to date, transport activity requires the coexpression of two distinct gene products, a predicted 340-amino acid, seven-transmembrane (TM) domain protein (OSTalpha) and a putative 128-amino acid, single-TM domain ancillary polypeptide (OSTbeta) [3].

Anatomical context of OSTbeta

• By coordinated control of OSTalpha/OSTbeta expression, bile acids may adjust the rate of their own efflux from enterocytes in response to changes in intracellular bile acid levels [4].
• Interestingly, OSTalpha and OSTbeta mRNAs were highly expressed and widely distributed in human tissues, with the highest levels occurring in the testis, colon, liver, small intestine, kidney, ovary, and adrenal gland [2].

Associations of OSTbeta with chemical compounds

• HepG2 cells treated for 24 h with chenodeoxycholic acid, a selective FXR ligand, had higher levels of OSTalpha and OSTbeta mRNA and protein [5].
• When OSTalpha and OSTbeta are coexpressed in Xenopus oocytes, they are able to mediate transport of estrone 3-sulfate, dehydroepiandrosterone 3- sulfate, taurocholate, digoxin, and prostaglandin E2, indicating a role in the disposition of key cellular metabolites or signaling molecules [3].

Physical interactions of OSTbeta

• In conclusion, the genes encoding the human OSTalpha/OSTbeta complex are induced by bile acids and FXR [4].

Other interactions of OSTbeta

• Although the transport function of OSTalpha/OSTbeta has been characterized, little is known about the regulation of its expression [4].
• The expression of OATP-A/1A2 and OSTbeta was also found in colon, but this was markedly decreased in neoplastic colon tissue [6].

References