Rab11, but not Rab4, facilitates cyclic AMP- and tauroursodeoxycholate-induced MRP2 translocation to the plasma membrane.

Rab proteins (Ras homologous for brain) play an important role in vesicle trafficking. Rab4 and Rab11 are involved in vesicular trafficking to the plasma membrane from early endosomes and recycling endosomes, respectively. Tauroursodeoxycholate (TUDC) and cAMP increase bile formation, in part, by increasing plasma membrane localization of multidrug resistance-associated protein 2 (MRP2). The goal of the present study was to determine the role of these Rab proteins in the trafficking of MRP2 by testing the hypothesis that Rab11 and/or Rab4 facilitate cAMP- and TUDC-induced MRP2 translocation to the plasma membrane. Studies were conducted in HuH-NTCP cells (HuH7 cells stably transfected with human NTCP), which constitutively express MRP2. HuH-NTCP cells were transfected with Rab11-WT and GDP-locked dominant inactive Rab11-GDP or with Rab4-GDP to study the role of Rab11 and Rab4. A biotinylation method and a GTP overlay assay were used to determine plasma membrane MRP2 and activation of Rab proteins (Rab11 and Rab4), respectively. Cyclic AMP and TUDC increased plasma membrane MRP2 and stimulated Rab11 activity. Plasma membrane translocation of MRP2 by cAMP and TUDC was increased and inhibited in cells transfected with Rab11-WT and Rab11-GDP, respectively. Cyclic AMP (previous study) and TUDC increased Rab4 activity. However, cAMP- and TUDC-induced increases in MRP2 were not inhibited by Rab4-GDP. Taken together, these results suggest that Rab11 is involved in cAMP- and TUDC-induced MRP2 translocation to the plasma membrane.