The organic anion transporting polypeptides OATP1B1 and OATP1B3 are two major drug transporters expressed in human hepatocytes. Because of their multispecificity, these two transporters are potential sites of adverse drug-drug interactions. In the previous grant period, we characterized substrate dependent modulation, identified molecular characteristics of the substrate binding sites, and identified several amino acid residues important for OATP1B1- and OATP1B3-mediated substrate transport. However, the molecular mechanisms responsible for their multispecificities remain unclear. Our long term research goal is to understand in detail the mechanism of OATP-mediated transport as an essential prerequisite to understanding, predicting, and preventing OATP-related adverse drug-drug interactions. The rationale for the proposed research is that, because OATP1B1 and OATP1B3 are critically involved in the liver's ability to clear numerous chemicals from the blood, improved mechanistic insights into their individual and overlapping transporter functions will provide a strong scientific framework for improvements in the prediction and prevention of adverse drug-drug interactions, as well as the future design of specific substrates and/or inhibitors of their transport activity. The objective of this application is to identify domains and amino acids that are important for substrate translocation and stimulation, and to characterize the driving force(s) for transport. Our central hypothesis is that OATP1B1 and OATP1B3 transport their substrates via a central pore that includes substrate-specific translocation pathways, and that OATP1B1 and OATP1B3 work as asymmetrical exchangers. We plan to test the hypothesis with two specific aims: 1) Identify and characterize the translocation pathways of OATP1B1 and OATP1B3;and 2) Determine the mechanism of OATP-mediated transport. Completion of these specific aims will explain the substrate dependent effects by identifying amino acids in the different transmembrane domains that influence substrate translocation and will lead us a step closer to the three dimensional structure of these membrane transporters. Furthermore, we will resolve the controversies of the transport mechanism, identify a physiological counter-anion, and explain the allosteric effects that might be due to the oligomeric state of the transporters. This contribution is significant because its results will provide the fundamental understanding required to predict OATP- mediated drug transport, ultimately leading to more effective and efficient therapies in addition to fundamentally advancing the field of organic anion transport.

Public Health Relevance

The proposed research is relevant to public health because a fundamental understanding of the structure/function relationships of OATP1B1 and OATP1B3 will provide the fundamental understanding required to predict OATP-mediated drug transport, ultimately leading to more effective and efficient therapies.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
2R01GM077336-05A1
Application #
8238101
Study Section
Xenobiotic and Nutrient Disposition and Action Study Section (XNDA)
Program Officer
Okita, Richard T
Project Start
2007-04-01
Project End
2015-11-30
Budget Start
2012-03-01
Budget End
2012-11-30
Support Year
5
Fiscal Year
2012
Total Cost
$302,000
Indirect Cost
$102,000
Name
University of Kansas
Department
Pharmacology
Type
Schools of Medicine
DUNS #
016060860
City
Kansas City
State
KS
Country
United States
Zip Code
66160
Steiner, Konstanze; Zimmermann, Lisa; Hagenbuch, Bruno et al. (2016) Zebrafish Oatp-mediated transport of microcystin congeners. Arch Toxicol 90:1129-39
Patik, Izabel; Kovacsics, Daniella; Német, Orsolya et al. (2015) Functional expression of the 11 human Organic Anion Transporting Polypeptides in insect cells reveals that sodium fluorescein is a general OATP substrate. Biochem Pharmacol 98:649-58
Tian, Jianan; Keller, Mark P; Oler, Angie T et al. (2015) Identification of the Bile Acid Transporter Slco1a6 as a Candidate Gene That Broadly Affects Gene Expression in Mouse Pancreatic Islets. Genetics 201:1253-62
Zhao, Wen; Zitzow, Jeremiah D; Ehresman, David J et al. (2015) Na+/Taurocholate Cotransporting Polypeptide and Apical Sodium-Dependent Bile Acid Transporter Are Involved in the Disposition of Perfluoroalkyl Sulfonates in Humans and Rats. Toxicol Sci 146:363-73
Woolbright, Benjamin L; Dorko, Kenneth; Antoine, Daniel J et al. (2015) Bile acid-induced necrosis in primary human hepatocytes and in patients with obstructive cholestasis. Toxicol Appl Pharmacol 283:168-77
Nieuweboer, Annemieke J M; Hu, Shuiying; Gui, Chunshan et al. (2014) Influence of drug formulation on OATP1B-mediated transport of paclitaxel. Cancer Res 74:3137-45
Steiner, Konstanze; Hagenbuch, Bruno; Dietrich, Daniel R (2014) Molecular cloning and functional characterization of a rainbow trout liver Oatp. Toxicol Appl Pharmacol 280:534-42
Ohnishi, Shuichi; Hays, Amanda; Hagenbuch, Bruno (2014) Cysteine scanning mutagenesis of transmembrane domain 10 in organic anion transporting polypeptide 1B1. Biochemistry 53:2261-70
Stieger, Bruno; Hagenbuch, Bruno (2014) Organic anion-transporting polypeptides. Curr Top Membr 73:205-32
Boxberger, Kelli H; Hagenbuch, Bruno; Lampe, Jed N (2014) Common drugs inhibit human organic cation transporter 1 (OCT1)-mediated neurotransmitter uptake. Drug Metab Dispos 42:990-5

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