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Molecular and Cellular Biology, May 2009, p. 2372-2389, Vol. 29, No. 9
0270-7306/09/$08.00+0 doi:10.1128/MCB.01505-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
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Department of Cell Biology, Faculty of Medicine, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan,1 Department of Immunology and Cell Biology, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan,2 Research Unit for Immune Surveillance, RIKEN Research Center for Allergy and Immunology, Yokohama, Kanagawa 230-0045, Japan,3 Division of Molecular and Cell Biology, Institute for Medical Science, Dokkyo University School of Medicine, Mibu-machi, Tochigi 321-0293, Japan,4 Laboratory of Biological Science, Graduate School of Frontier Biosciences/Department of Pathology, Graduate School of Medicine, Osaka University, Suita, Osaka 565-0871, Japan,5 Division of Cellular and Molecular Medicine, Kobe University Graduate School of Medicine, Chuo-ku, Kobe 650-0017, Japan6
Received 26 September 2008/ Returned for modification 27 October 2008/ Accepted 17 February 2009
MUPP1 and Patj are both composed of an L27 domain and multiple PDZ domains (13 and 10 domains, respectively) and are localized to tight junctions (TJs) in epithelial cells. Although Patj is known to be responsible for the organization of TJs and epithelial polarity, characterization of MUPP1 is lacking. In this study, we found that MUPP1 and Patj share several binding partners, including JAM1, ZO-3, Pals1, Par6, and nectins (cell-cell adhesion molecules at adherens junctions). MUPP1 and Patj exhibited similar subcellular distributions, and the mechanisms with which they localize to TJs also appear to overlap. Despite these similarities, functional studies have revealed that Patj is indispensable for the establishment of TJs and epithelial polarization, whereas MUPP1 is not. Thus, although MUPP1 and Patj share several molecular properties, their functions are entirely different. We present evidence that the signaling mediated by Pals1, which has a higher affinity for Patj than for MUPP1 and is involved in the activation of the Par6-aPKC complex, is of principal importance for the function of Patj in epithelial cells.
Published ahead of print on 2 March 2009.
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