Disturbed colocalization of multidrug resistance protein 2 and radixin in human cholestatic liver diseases.
OBJECTIVE
Endocytic retrieval of multidrug resistance protein 2 (MRP2) is closely associated with cholestasis and may be attributed to the disturbed linking of MRP2 and radixin, a cross-linker between actin filaments and membrane proteins. This study aimed to investigate the role of radixin in the altered localization of MRP2 in various human cholestatic liver diseases.


METHODS
Using immunofluorescence microscopy, we investigated the localization and expression of MRP2 and radixin in various cholestatic liver diseases, such as drug-induced liver injury, obstructive jaundice, primary sclerosing cholangitis and autoimmune hepatitis. Changes in localization and expression were analyzed using Scion Image (software).


RESULTS
In the icteric drug-induced liver injury, MRP2 was localized outside as well as inside of ZO-1 staining, indicating endocytic retrieval from the canalicular membrane into the pericanalicular compartments of the hepatocytes. The colocalization of MRP2 and radixin observed in the controls was disturbed, and MRP2 fluorescence disappeared in the canaliculi with disrupted radixin staining. Disturbed colocalization of MRP2 and radixin as well as endocytic retrieval of MRP2 was found in the poorly drained obstructive jaundice. When drainage was good, MRP2 was exclusively colocalized with radixin. Similar findings were observed in autoimmune hepatitis and primary sclerosing cholangitis. In the controls, the immunostaining intensity curves for MRP2 and radixin were steeply elevated in the canaliculi. The intensity curves for MRP2 and radixin were broadened in the icteric drug-induced liver injury and poorly drained obstructive jaundice, indicating endocytic retrieval into the hepatocytes. The peak fluorescence intensities for MRP2 and radixin decreased in the icteric liver.


CONCLUSIONS
Disturbed colocalization of MRP2 and radixin was common in various cholestatic liver diseases, which may be associated with endocytic retrieval of MRP2 due to failure in anchoring MRP2 in the canalicular membrane.
Kojima
Hideyuki
H
Third Department of Internal Medicine, Nara Medical University, Kashihara, Japan. kojima@nmu-gw.naramed-u.ac.jp
Sakurai
Shinya
S
Uemura
Masahito
M
Kitamura
Kensuke
K
Kanno
Hiroki
H
Nakai
Yoshiyuki
Y
Fukui
Hiroshi
H
D000328:Adult; D000368:Aged; D001648:Bile Canaliculi / Q000737:chemistry; D016022:Case-Control Studies; D002779:Cholestasis / Q000150:complications* / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000032:analysis*; D004705:Endocytosis; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008099:Liver / Q000737:chemistry*; D008107:Liver Diseases / Q000209:etiology / Q000378:metabolism*; D008297:Male; D008565:Membrane Proteins / Q000032:analysis*; D008856:Microscopy, Fluorescence; D008875:Middle Aged; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000032:analysis*; D010750:Phosphoproteins / Q000032:analysis; D021381:Protein Transport; D062826:Zonula Occludens-1 Protein
D003598:Cytoskeletal Proteins; D008565:Membrane Proteins; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D010750:Phosphoproteins; D062826:Zonula Occludens-1 Protein; C000715087:ABCC2 protein, human; C569042:TJP1 protein, human; C071776:radixin