Please use this identifier to cite or link to this item:
|Title:||Human organic anion transporter 1B1 and 1B3 function as bidirectional carriers and do not mediate GSH-bile acid cotransport|
Steven M. Grassl
State University of New York Upstate Medical University
University of Rochester School of Medicine and Dentistry
|Keywords:||Biochemistry, Genetics and Molecular Biology;Medicine|
|Citation:||American Journal of Physiology - Gastrointestinal and Liver Physiology. Vol.293, No.1 (2007)|
|Abstract:||Organic anion transporting polypeptides (OATP/SLCO) are generally believed to function as electroneutral anion exchangers, but direct evidence for this contention has only been provided for one member of this large family of genes, rat Oatp1a1/Oatp1 (Slco1a1). In contrast, a recent study has indicated that human OATP1B3/OATP-8 (SLCO1B3) functions as a GSH-bile acid cotransporter. The present study examined the transport mechanism and possible GSH requirement of the two members of this protein family that are expressed in relatively high levels in the human liver, OATP1B3/OATP-8 and OATP1B1/OATP-C (SLCO1B1). Uptake of taurocholate in Xenopus laevis oocytes expressing either OATP1B1/OATP-C, OATP1B3/OATP-8, or polymorphic forms of OATP1B3/OATP-8 (namely, S112A and/or M233I) was cis-inhibited by taurocholate and estrone sulfate but was unaffected by GSH. Likewise, taurocholate and estrone sulfate transport were trans-stimulated by estrone sulfate and taurocholate but were unaffected by GSH. OATP1B3/OATP-8 also did not mediate GSH efflux or GSH-taurocholate cotransport out of cells, indicating that GSH is not required for transport activity. In addition, estrone sulfate uptake in oocytes microinjected with OATP1B3/OATP-8 or OATP1B1/OATP-C cRNA was unaffected by depolarization of the membrane potential or by changes in pH, suggesting an electroneutral transport mechanism. Overall, these results indicate that OATP1B3/OATP-8 and OATP1B1/OATP-C most likely function as bidirectional facilitated diffusion transporters and that GSH is not a substrate or activator of their transport activity. Copyright © 2007 the American Physiological Society.|
|Appears in Collections:||Scopus 2006-2010|
Files in This Item:
There are no files associated with this item.
Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.