Factors Affecting Multidrug Resistance Protein 4 Expression and Function
ATP-binding cassette (ABC) transporters are a superfamily of membrane proteins responsible for the import and export of a variety of xenobiotics and endogenous compounds. Multidrug resistance protein 4 (MRP4) is an ABC transporter expressed in a number of human tissues. MRP4 has a number of genetic variants, but the impact of many of these variants is unknown. First, we used Western blotting and fluorescence microscopy to examine the effect of a number of genetic variants on MRP4 expression and localization, identifying a number of variants with reduced expression. Next, we developed a membrane vesicle assay to examine the effect of phosphodiesterase inhibitors on MRP4 transport of the model substrate leukotriene C4.