| Project/Area Number |
17590669
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Gastroenterology
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| Research Institution | Nara Medical University |
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Principal Investigator |
KOJIMA Hideyuki Nara Medical University, Third Department of Internal Medicine, Assistant doctor, 医学部, 助手 (60326345)
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| Co-Investigator(Kenkyū-buntansha) |
YOSHIJI Hitoshi Nara Medical University, Third Department of Internal Medicine, Assistant doctor, 医学部, 助手 (40336855)
YAMAO Jun-ichi Nara Medical University, Third Department of Internal Medicine, Lecturer, 医学部, 講師 (10221649)
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| Project Period (FY) |
2005 – 2006
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| Project Status |
Completed (Fiscal Year 2006)
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| Budget Amount *help |
¥2,600,000 (Direct Cost: ¥2,600,000)
Fiscal Year 2006: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 2005: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Keywords | cholestasis / radixin / phosphorylation / crosslinker / transporter protein / canalicular export pump / multidrug export pump / endocytic retrieval / multidrug resistance protein2 |
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| Research Abstract |
Cholestasis has been associated with endocytic retrieval of multidrug resistance protein 2 (Mrp2), but its mechanism is still unclear. Recent studies have indicated that radixin, a cross-linker between the actin filaments and membrane proteins, may be activated by phosphorylation, and be required for the canalicular localization of Mrp2. We investigated the role of radixin in the altered localization of Mrp2 in the rat models of intrahepatic (ethinyl estradiol treatment) and extrahepatic cholestasis (bile duct ligation) using immunofluorescence microscopy. The changes in localization and expression were analyzed using the Scion Image. In both models, Mrp2 was localized outside as well as inside the ZO-1 staining, indicating the partial dislocation from the canalicular membrane. In contrast to the steep elevation of the immunostaining intensity curves for Mrp2 in the controls, the corresponding curves in both models were broadened and flattened, confirming endocytic retrieval into the hepatocytes. Mrp2 and radixin were colocalized at the canalicular domain in the controls, whereas those in both cholestatic rats were dissociated at some canaliculi, indicating the disturbed colocalization of Mrp2 and radixin in cholestasis. The fluorescence of phosphorylated radixin, an active form of radixin, markedly decreased in both cholestatic models, which was supported by the reduced peak fluorescence intensities. In conclusion, the disturbed colocalization of Mrp2 and radixin may contribute to endocytic retrieval of Mrp2 in cholestasis due to failure in anchoring Mrp2 in the canalicular membrane, in which the phosphorylated radixin may play a major role.
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