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J. Biol. Chem., Vol. 281, Issue 19, 13300-13308, May 12, 2006
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1
2

3
From the
Department of Pharmacology, School of Pharmacy, Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem 91120, Israel and the
Department of Cell Biology, University of Virginia Health Sciences Center, Charlottesville, Virginia 22908
ARNO is a guanine-nucleotide exchange protein for the ARF family of GTPases. Here we show that in polarized epithelial cells, ARNO is localized exclusively to the apical plasma membrane, where it regulates endocytosis. Expression of ARNO stimulates apical endocytosis of the polymeric immunoglobulin receptor, and coexpression of ARF6 with ARNO leads to a synergistic stimulation of apical endocytosis. Expression of a dominant negative ARF6 mutant, ARF6-T27N, antagonizes this stimulatory effect. Deletion of the N-terminal coiled-coil (CC) domain of ARNO causes the mutant ARNO to localize to both the apical and basolateral plasma membranes. Expression of the CC domain alone abolishes ARNO-induced apical endocytosis as well as co-localization of IgA-receptor complexes with ARNO and clathrin. These results suggest that the CC domain contributes to the specificity of apical localization of ARNO through association with components of the apical plasma membrane. We conclude that ARNO acts together with ARF6 to regulate apical endocytosis.
Received for publication, December 27, 2005 , and in revised form, February 15, 2006.
* This work was supported by Israel Science Foundation Grant 1318/04 (to Y. A.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
1 Present address: Dept. of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA 16804-3000.
2 Present address: Children's Hospital Boston, Boston, MA 02115.
3 To whom correspondence should be addressed: Dept. of Pharmacology, School of Pharmacy, Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem 91120, Israel. Tel.: 972-2-6757578; Fax: 972-2-6758927; E-mail: yoram11{at}md.huji.ac.il.
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