Ajuba family LIM proteins localize to and play important roles at cell-cell and cell matrix adhesions in epithelial and fibroblast cells, respectively. In addition, these proteins shuttle to the nucleus, suggesting that they may coordinate cell surface events with nuclear responses. Little is known, however, about the mechanism by which these proteins shuttle or the biological consequences of their nuclear localization. Here, we have identified the Snail family of zinc finger transcriptional repressors as functional interactors of the Ajuba LIM proteins. We show that Ajuba LIM proteins interact with Snail proteins in the nucleus, contribute to Snail-dependent repression of E-cadherin, and are present on endogenous E-cadherin promoters in the presence of Snail. Using Xenopus neural crest as a model of in vivo Snail- or Slug (Snail2)-induced epithelial mesenchymal transitions (EMT), we demonstrate that Ajuba LIM proteins contribute to neural crest development in a Slug-dependent manner. In addition, we show that interaction with Ajuba LIM proteins is essential for Snail- or Slug-mediated neural crest development. These data indicate that Ajuba LIM proteins are Snail family corepressors required for in vivo Snail function. Using P19 embryonal carcinoma cells, we also investigate the mechanism by which Ajuba affects endodermal and neuronal differentiation, processes which are regulated by Snail family members. We provide a model in which Ajuba interacts with Snail family proteins via its LIM domains, while its N-terminal preLIM region functions to recruit a functional repressor complex. In summary, Ajuba LIM proteins not only participate in junction assembly or stability as components of cell-cell junctions in epithelia, but also contribute to EMT through a functional interaction with Snail proteins in the nucleus. These opposing functions suggest that Ajuba LIM proteins, through regulation of their subcellular localization and interacting partners, are important regulators of epithelia dynamics.A. Myc-tagged LIM proteins and Flag-tagged Snail were cotransfected into HEK293 cells. ... members and Ajuba or Zyxin family members, as determined using the method described in A. C. Top: Schematic diagram of Ajuba constructs used.
|Title||:||The Role of Ajuba LIM Proteins in the Nucleus|
|Author||:||Ellen Marie Langer|
|Publisher||:||ProQuest - 2007|