Abstract
The ABC transporters multidrug resistance associated protein 2 (MRP2) and breast cancer resistance protein (BCRP) are of interest in drug development, since they affect the pharmacokinetics of several drugs. Membrane vesicle transport assays are widely used to study interactions with these proteins. Since albumin has been found to affect the kinetics of metabolic enzymes in similar membrane preparations, we investigated whether albumin affects the kinetic parameters of efflux transport. We found that albumin increased the Vmax of 5(6)-carboxy-2’,7’-dichlorofluorescein (CDCF) and estradiol-17-β-D-glucuronide uptake into MRP2 vesicles in the presence of 0.1% bovine serum albumin (BSA) by 2 and 1.5-fold, respectively, while BSA increased Lucifer yellow uptake by 30% in BCRP vesicles. Km values increased slightly, but the change was not statistically significant. The effect of BSA on substrate uptake was dependent on the vesicle amount, while increasing BSA concentration did not significantly improve substrate uptake. These results indicate a minor effect of albumin on MRP2 and BCRP, but it should be considered if albumin is added to transporter assays for example as a solubilizer, since the effect may be substrate or transporter specific.
Highlights
ATP-binding cassette proteins, known as ABC proteins or ABC transporters, are a large group of membrane proteins that translocate a wide range of substrates across various biological membranes using ATP as energy [1]
Due to the similarity of the preparations used to study the metabolic enzymes and the transporters that may affect drug pharmacokinetics, we investigated whether bovine serum albumin (BSA) has an effect on the observed ATP-dependent transport of the ABC transporters multidrug resistance associated protein 2 (MRP2) and breast cancer resistance protein (BCRP) in the vesicular transport assay and if the effect could potentially be mediated by fatty acids as has been proposed for the metabolic enzymes
Our results show that the BSA effect for MRP2 and BCRP is displayed mainly through changes in Vmax
Summary
ATP-binding cassette proteins, known as ABC proteins or ABC transporters, are a large group of membrane proteins that translocate a wide range of substrates across various biological membranes using ATP as energy [1]. ABC transporters have an important role in the disposition and elimination of endogenous compounds and the defense of the cell against xenobiotics. Among the ABC transporters implicated in drug transport are the multidrug resistance associated protein 2 (MRP2) and the breast cancer resistance protein (BCRP) or ABCC2 and ABCG2, respectively, according to ABC nomenclature. They are involved in drug efflux in several tissues, including the liver, intestine and kidney [2,3,4,5]. Dysfunction of the protein results in the accumulation of PLOS ONE | DOI:10.1371/journal.pone.0163886 October 5, 2016
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