Multidrug resistance-associated protein 2 (Mrp2) is an
ATP-dependent export pump that mediates the formation of
bile-salt-independent bile flow. Disruption of the canalicular localization of Mrp2, without changes in its expression, is observed in
chronic liver failure and is accompanied by oxidative stress. We reported previously that Mrp2 is rapidly internalized from the canalicular membrane during acute oxidative stress induced by
lipopolysaccharide (LPS) in the rat liver. A disturbance in the colocalization of Mrp2 and
radixin (which crosslinks actin with interacting
membrane proteins) and endocytic retrieval of Mrp2 are present in
chronic liver failure. However, the C-terminal phosphorylation status of
radixin (p-
radixin; functional form) and its
protein-
protein interaction with Mrp2 were not examined in the pathological cholestatic situation. In this study, we examined whether the C-terminal phosphorylation status of
radixin and its interaction with Mrp2 were affected by LPS-induced experimental
liver failure with
cholestasis, and whether this condition was accompanied by Mrp2 internalization in the rat liver. At 3h after LPS treatment, the canalicular expression of Mrp2 was decreased, without variation of the other canalicular transporters. Similarly, the canalicular localization of
radixin was decreased after LPS treatment. These results show that LPS treatment decreased the total amount of the active form of p-
radixin and the amount of
radixin that coimmunoprecipitated with Mrp2, and that LPS treatment impaired the
protein-
protein interaction between Mrp2 and
radixin. In conclusion, LPS-induced
cholestasis seems to be caused by posttranscriptional regulation of Mrp2, which is due to the disruption of its interaction with
radixin and by its dephosphorylation.