title: H-Ras activation promotes cytoplasmic accumulation and phosphoinositide 3-OH kinase association of beta-catenin in epidermal keratinocytes.
abstract: The mechanisms underlying downregulation of the cadherin/catenin complexes and beta-catenin signaling during tumor progression are not fully understood. We have analyzed the effect of oncogenic H-Ras on E-cadherin/catenin complex formation/stabilization and beta-catenin distribution in epidermal keratinocytes. Microinjection or stable expression of V12Ras into keratinocytes promotes the loss of E-cadherin and alpha-catenin and relocalization of beta-catenin to the cytoplasm and nucleus. Moreover, these effects are dependent on PI3K (phosphoinositide 3-OH kinase) activity. Interestingly, a strong association of p85alpha and p110alpha subunits of PI3K with beta-catenin is induced in V12Ras-expressing keratinocytes, and in vitro binding assays show a direct interaction between beta-catenin and p85alpha. Overexpression of either V12Ras or constitutively active p110alpha induces metabolic stabilization of beta-catenin and promotes its accumulation in cytoplasmic and nuclear pools. In addition, the interaction of beta-catenin with the adenomatous polyposis coli protein is blocked in V12Ras and p110alpha transformants though no changes in glycogen synthase kinase 3 beta activity could be detected. Nevertheless, in V12Ras transformants the in vivo phosphorylation of beta-catenin in Ser residues is strongly decreased. These results indicate that H-Ras activation induces the relocalization and cytoplasmic stabilization of beta-catenin by a mechanism involving its interaction with PI3K.
authors.affiliation: Instituto de Investigaciones Biomédicas, Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, 28029 Madrid, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Espada
authors.forename: M
authors.initials: M
authors.lastname: Pérez-Moreno
authors.forename: V M
authors.initials: VM
authors.lastname: Braga
authors.forename: P
authors.initials: P
authors.lastname: Rodriguez-Viciana
authors.forename: A
authors.initials: A
authors.lastname: Cano
mesh_terms: D025601:Adenomatous Polyposis Coli Protein; D000818:Animals; D015820:Cadherins / Q000378:metabolism; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D002471:Cell Transformation, Neoplastic; D003593:Cytoplasm / Q000378:metabolism*; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D004789:Enzyme Activation; D038362:Glycogen Synthase Kinase 3; D038341:Glycogen Synthase Kinases; D015603:Keratinocytes / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D051379:Mice; D008845:Microinjections; D015689:Oncogene Protein p21(ras) / Q000235:genetics / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D010768:Phosphoserine / Q000032:analysis / Q000378:metabolism; D019000:Phosphotyrosine / Q000032:analysis; D011485:Protein Binding; D015534:Trans-Activators; D051178:alpha Catenin; D051176:beta Catenin
chemical_list: D025601:Adenomatous Polyposis Coli Protein; D015820:Cadherins; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D003598:Cytoskeletal Proteins; D038362:Glycogen Synthase Kinase 3; D038341:Glycogen Synthase Kinases; D015689:Oncogene Protein p21(ras); D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010768:Phosphoserine; D019000:Phosphotyrosine; D015534:Trans-Activators; D051178:alpha Catenin; D051176:beta Catenin; C495267:CTNNB1 protein, mouse; C495272:Ctnna1 protein, mouse