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Radixin deficiency causes conjugated hyperbilirubinemia with loss of Mrp2 from bile canalicular membranes

Nature Genetics volume 31, pages 320–325 (2002)Cite this article

Abstract

The ezrin-radixin-moesin (ERM) family of proteins crosslink actin filaments and integral membrane proteins1,2,3. Radixin (encoded by Rdx) is the dominant ERM protein in the liver of wildtype mice4,5 and is concentrated at bile canalicular membranes (BCMs)5. Here we show that Rdx−/− mice are normal at birth, but their serum concentrations of conjugated bilirubin begin to increase gradually around 4 weeks, and they show mild liver injury after 8 weeks. This phenotype is similar to human conjugated hyperbilirubinemia in Dubin-Johnson syndrome6,7, which is caused by mutations in the multidrug resistance protein 2 (MRP2, gene symbol ABCC2)8,9,10,11, although this syndrome is not associated with overt liver injury. In wildtype mice, Mrp2 concentrates at BCMs to secrete conjugated bilirubin into bile8,11,12. In the BCMs of Rdx−/− mice, Mrp2 is decreased compared with other BCM proteins such as dipeptidyl peptidase IV (CD26) and P-glycoproteins. In vitro binding studies show that radixin associates directly with the carboxy-terminal cytoplasmic domain of human MRP2. These findings indicate that radixin is required for secretion of conjugated bilirubin through its support of Mrp2 localization at BCMs.

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Figure 1: Targeted disruption of Rdx in ES cells and generation of radixin-deficient mice.
Figure 2: Increase of bilirubin and enzyme activities in sera of Rdx−/− mice.
Figure 3: Selective loss of Mrp2 from BCMs in Rdx−/− mice.
Figure 4: Ultrathin-section and scanning electron micrographs of the liver of wildtype and Rdx−/− mice at 2 wk (a) and 16 wk (b).
Figure 5: Association of Mrp2 with ERM proteins.

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Acknowledgements

We thank T. Noda for discussions and J. Yamane for preparing bile canalicular fractions. This work was supported in part by a Grant-in-Aid for Scientific Research (B) (to Sa.T.) and a Grant-in-Aid for Cancer Research (to Sh.T.) from the Ministry of Education, Science and Culture of Japan, and grants from the Deutsche Forschunggemeinshaft (to D.K.).

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  1. Shojiro Kikuchi and Masaki Hata: These authors contributed equally to this work.

Authors and Affiliations

  1. Department of Cell Biology, Faculty of Medicine, Kyoto University, Sakyo-ku, Kyoto, 606-8501, Japan

    Shojiro Kikuchi, Kanehisa Fukumoto, Yukari Yamane, Takeshi Matsui, Atsushi Tamura, Shoichiro Tsukita & Sachiko Tsukita

  2. Department of Surgery, Kyoto Prefectural University of Medicine, Kamigyo-ku, Kyoto, 602-8566, Japan

    Shojiro Kikuchi, Kanehisa Fukumoto & Hisakazu Yamagishi

  3. KAN Research Institute, Kyoto Research Park, Shimogyo-ku, Kyoto, 600-8815, Japan

    Masaki Hata & Takeshi Matsui

  4. Laboratory for Cellular Morphogenesis, RIKEN Center for Developmental Biology, Chuo-ku, Kobe, 650-0047, Japan

    Shigenobu Yonemura

  5. Division of Tumor Biochemistry, Deutsches Krebsforschungszentrum, Heidelberg, D-69120, Germany

    Dietrich Keppler

  6. College of Medical Technology, Kyoto University, Sakyo-ku, Kyoto, 606-8507, Japan

    Sachiko Tsukita

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Correspondence to Sachiko Tsukita.

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Kikuchi, S., Hata, M., Fukumoto, K. et al. Radixin deficiency causes conjugated hyperbilirubinemia with loss of Mrp2 from bile canalicular membranes. Nat Genet 31, 320–325 (2002). https://doi.org/10.1038/ng905

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