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The keratin-binding protein Albatross regulates polarization of epithelial cells

¹ Division of Biochemistry, Aichi Cancer Center Research Institute, Chikusa-ku, Nagoya 464-8681, Japan
² Department of Cell Pharmacology and ³ Department of Cellular Oncology, Graduate School of Medicine, Nagoya University, Showa-ku, Nagoya 466-8550, Japan
⁴ RIKEN Center for Developmental Biology, Chuo-ku, Kobe 650-0047, Japan
⁵ Department of Ophthalmology, Mie University Faculty of Medicine, Tsu, Mie 514-8507, Japan
⁶ Virology Division, National Cancer Center Research Institute, Chuo-ku, Tokyo 104-0045, Japan

Correspondence to Masaki Inagaki: minagaki{at}aichi-cc.jp

The keratin intermediate filament network is abundant in epithelial cells, but its function in the establishment and maintenance of cell polarity is unclear. Here, we show that Albatross complexes with Par3 to regulate formation of the apical junctional complex (AJC) and maintain lateral membrane identity. In nonpolarized epithelial cells, Albatross localizes with keratin filaments, whereas in polarized epithelial cells, Albatross is primarily localized in the vicinity of the AJC. Knockdown of Albatross in polarized cells causes a disappearance of key components of the AJC at cell–cell borders and keratin filament reorganization. Lateral proteins E-cadherin and desmoglein 2 were mislocalized even on the apical side. Although Albatross promotes localization of Par3 to the AJC, Par3 and ezrin are still retained at the apical surface in Albatross knockdown cells, which retain intact microvilli. Analysis of keratin-deficient epithelial cells revealed that keratins are required to stabilize the Albatross protein, thus promoting the formation of AJC. We propose that keratins and the keratin-binding protein Albatross are important for epithelial cell polarization.

Abbreviations used in this paper: AJ, adherens junctions; AJC, apical junctional complex; BC, bile canaliculi; DS, desmosomes; GAPDH, glyceraldehyde 3-phosphate dehydrogenase; IF, intermediate filament; K8/18, keratin 8 and 18; MBP, maltose-binding protein; TJ, tight junctions; TPHD, trichohyalin and plectin homology domain.

© 2008 Sugimoto et al. This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.jcb.org/misc/terms.shtml). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 3.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/3.0/).

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