Inducible expression of p120Cas1B isoform corroborates the role for p120-catenin as a positive regulator of E-cadherin function in intestinal cancer cells q Santiago Roura * and David Dom  ınguez Unitat de Biologia Cellular i Molecular, Institut Municipal d’Investigaci o M edica, Universitat Pompeu Fabra, 08003 Barcelona, Spain Received 24 May 2004 Available online Abstract Over the past decade, the exact function of p120-catenin in regulation of E-cadherin/catenins complex has remained particularly controversial. We have previously reported that E-cadherin-mediated adhesion is tightly regulated by tyrosine phosphorylation of catenins. However, this effect is not observed in human colon carcinoma cell line Caco-2. Here, we have generated inducible Caco-2 clones that display p120Cas1B, a p120-catenin isoform poorly expressed by these cells. As a result, neither expression of the transgene nor tyrosine phosphorylation of catenins induces redistribution of E-cadherin to the cytosol and disassembly of adherens and tight junctions. In contrast, E-cadherin appears markedly increased reinforcing cell–cell adhesion. Interestingly, a substantial decrease in p120-catenin levels is found in MDCK cells expressing Snail, in which E-cadherin expression is strongly inhibited. Additionally, we show that the specific depletion of p120-catenin decreases cell–cell contacts, and increases cell motility and scat- tering of colonies established by HT-29 M6 cells. Together our results corroborate that p120-catenin plays an essential role in the maintenance of the required E-cadherin protein levels that prevent the loss of epithelial characteristics occurred during tumori- genesis. Ó 2004 Elsevier Inc. All rights reserved. Keywords: p120-Catenin; b-Catenin; Cell–cell adhesion; Monolayer permeability; E-cadherin; Tyrosine phosphorylation The adhesive function of E-cadherin, the predomi- nant cadherin in epithelial cells and responsible for the correct establishment and maintenance of adherens junctions (AJs), requires the role of a set of proteins collectively named catenins [1]. The members of this extended family mediate E-cadherin attachment to actin cytoskeleton [2,3]. p120-catenin, also referred to as p120Cas (cadherin-associated Src substrate), was origi- nally identified as a major target for this oncogenic ty- rosine kinase [4]. Similar to b-catenin, p120-catenin shows constitutive tyrosine phosphorylation during malignant transformation suggesting a strong relation- ship between these cell phenomena. Despite the clear association of p120-catenin with E- cadherin adhesion complex, its possible contribution to tumor cell adhesion, motility, and invasion remains controversial, although it seems to be fundamentally different from that of b-catenin. Both catenins are structurally similar but do not bind to the same region of cytosolic domain of E-cadherin [5]; unlike b-catenin, p120-catenin does not interact with a-catenin nor the tumor suppressor protein adenomatous polyposis coli (APC) [5] and is expressed, in cell-type specific patterns, as multiple isoforms by alternative splicing between three different exons (A, B, and C) and four ATG start sites (1, 2, 3, and 4) [6]. Relating to how p120-catenin regulates E-cadherin function, laboratory studies indicate that it directly participates in clustering of q Abbreviations: AJ, adherens junction; TJ, tight junction; p120Cas, p120 cadherin-associated Src substrate; VaO 4 Na 3 , sodium orthovanadate. * Corresponding author. Present address: Laboratori de Fisiologia Cellular, Servei de Cardiologia, Hospital de la Santa Creu i Sant Pau, C/Sant Antoni M a Claret 167, 08025 Barcelona, Spain. Fax: +34-93- 291-94-24. E-mail address: sroura@hsp.santpau.es (S. Roura). 0006-291X/$ - see front matter Ó 2004 Elsevier Inc. All rights reserved. doi:10.1016/j.bbrc.2004.05.186 Biochemical and Biophysical Research Communications 320 (2004) 435–441 BBRC www.elsevier.com/locate/ybbrc