Gosens Ilse, Sessa Alessandro, den Hollander Anneke I, Letteboer Stef J F, Belloni Valentina, Arends Maarten L, Le Bivic André, Cremers Frans P M, Broccoli Vania, Roepman Ronald
Department of Human Genetics, Radboud University Nijmegen Medical Centre, Geert Grooteplein Zuid 10, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands.
Exp Cell Res. 2007 Nov 15;313(19):3959-70. doi: 10.1016/j.yexcr.2007.08.025. Epub 2007 Sep 7.
Cell polarity is induced and maintained by separation of the apical and basolateral domains through specialized cell-cell junctions. The Crumbs protein and its binding partners are involved in formation and stabilization of adherens junctions. In this study, we describe a novel component of the mammalian Crumbs complex, the FERM domain protein EPB41L5, which associates with the intracellular domains of all three Crumbs homologs through its FERM domain. Surprisingly, the same FERM domain is involved in binding to the HOOK domain of MPP5/PALS1, a previously identified interactor of Crumbs. Co-expression and co-localization studies suggested that in several epithelial derived tissues Epb4.1l5 interacts with at least one Crumbs homolog, and with Mpp5. Although at early embryonic stages Epb4.1l5 is found at the basolateral membrane compartment, in adult tissues it co-localizes at the apical domain with Crumbs proteins and Mpp5. Overexpression of Epb4.1l5 in polarized MDCK cells affects tightness of cell junctions and results in disorganization of the tight junction markers ZO-1 and PATJ. Our results emphasize the importance of a conserved Crumbs-MPP5-EPB41L5 polarity complex in mammals.
细胞极性是通过特殊的细胞-细胞连接来诱导和维持顶端和基底外侧结构域的分离而形成的。Crb蛋白及其结合伙伴参与黏着连接的形成和稳定。在本研究中，我们描述了哺乳动物Crb复合体的一个新组分，即FERM结构域蛋白EPB41L5，它通过其FERM结构域与所有三种Crb同源物的胞内结构域结合。令人惊讶的是，同一个FERM结构域还参与与MPP5/PALS1的HOOK结构域结合，MPP5/PALS1是之前鉴定出的Crb相互作用蛋白。共表达和共定位研究表明，在几种上皮来源的组织中，Epb4.1l5与至少一种Crb同源物以及Mpp5相互作用。尽管在胚胎早期阶段，Epb4.1l5定位于基底外侧膜区室，但在成年组织中，它与Crb蛋白和Mpp5共定位于顶端结构域。在极化的MDCK细胞中过表达Epb4.1l5会影响细胞连接的紧密性，并导致紧密连接标记物ZO-1和PATJ的紊乱。我们的结果强调了保守的Crb-MPP5-EPB41L5极性复合体在哺乳动物中的重要性。
