TY - JOUR T1 - OATP1B3 expression and function is modulated by co-expression with OCT1, OATP1B1, and NTCP JF - Drug Metabolism and Disposition JO - Drug Metab Dispos DO - 10.1124/dmd.119.089847 SP - dmd.119.089847 AU - Yuchen Zhang AU - Melissa Ruggiero AU - Bruno Hagenbuch Y1 - 2020/01/01 UR - http://dmd.aspetjournals.org/content/early/2020/06/01/dmd.119.089847.abstract N2 - OATP1B3 is a drug transporter expressed at the basolateral membrane of human hepatocytes. Along with other transporters, including OATP1B1, NTCP, and OCT1, it is responsible for the uptake of endo- and xenobiotics into hepatocytes. Our previous studies demonstrated that OATP1B3 can form hetero-oligomers, with OATP1B1 in HEK293 cells and with NTCP in both HEK293 cells and frozen human liver sections. To further characterize the hetero-oligomerization of OATP1B3, we investigated OCT1 as a potential interacting partner and determined the functional consequences of OATP1B3 hetero-oligomerization. We demonstrated interactions between OATP1B3 and OCT1 by co-immunoprecipitation with an anti-OATP1B3 antibody from human hepatocytes. In addition, we visualized the interaction using the Proximity Ligation Assay in both HEK293 cells and in frozen human liver sections. We investigated the functional consequences of OATP1B3 hetero-oligomerization by measuring the OATP1B3 plasma membrane expression and the uptake of the OATP1B3 selective substrate cholecystokinin-8 (CCK-8) in the absence and presence of OATP1B1, NTCP and OCT1. A significant decrease of OATP1B3 plasma membrane expression was observed after co-expression with OCT1, while co-expression with OATP1B1 or NTCP resulted in an increase of plasma membrane expression. With respect to transport, co-expression of OCT1 increased the apparent turnover rate (kcat) of OATP1B3 while co-expression of OATP1B1 or NTCP decreased it. These findings demonstrated that co-expression of OATP1B3 with OATP1B1, NTCP, and OCT1 in HEK293 cells results in a transporter-dependent modification of OATP1B3-mediated CCK-8 transport and suggest that functional results obtained in single transporter over-expressing cell lines over- or underestimate OATP1B3 function in human hepatocytes.SIGNIFICANCE STATEMENT Co-expression of OATP1B3 with OCT1, NTCP or OATP1B1 in HEK293 cells affects its expression level and function. When OCT1 is knocked down in human hepatocytes function of OATP1B3 goes up. These results suggest that protein-protein interactions can affect the expression and function of the involved proteins and thus single transporter expression systems might lead to over- or underestimation of drug-drug interactions. ER -