title: Modulation of alpha-catenin Tyr phosphorylation by SHP2 positively effects cell transformation induced by the constitutively active FGFR3.
abstract: The Src homology 2 phosphotyrosyl phosphatase (SHP2) is a nonreceptor-type phosphatase that acts as a positive transducer of receptor Tyr kinase (RTK) signaling, particularly the Ras-REK and PI3K-Akt pathways. Recently, we have demonstrated that SHP2 is required for cell transformation induced by the constitutively active fibroblast growth factor receptor 3 (K/E-FR3) (Oncogene, 22, 6909-6918). In that study, we had detected a phosphotyrosyl protein of approximately 100 KDa (p100) in cells expressing dominant-negative SHP2 (R/E-SHP2), but its identity and relevance in SHP2-meditaed transformation was not known. Here, we report the identification of p100 as alpha-catenin, a vinculin-related protein involved in adherens junction-mediated intercellular adhesion. We show that alpha-catenin becomes Tyr phosphorylated in intercellular adhesion-dependent manner and this event is counteracted by SHP2. Substrate trapping in intact cells and immunocomplex phosphatse assays confirmed that alpha-catenin is in deed an SHP2 substrate. Tyr phosphorylation of alpha-catenin enhances its translocation to the plasma membrane and its interaction with beta-catenin, leading to enhanced actin polymerization and stabilization of adherens junction-mediated intercellular adhesion, a phenomenon commensurate with loss of the transformation phenotype. Site-directed mutagenesis studies also suggested that Tyr phosphorylation of alpha-catenin enhances its inhibitory role on cell transformation. Based on our previous work and the current report, we demonstrate that mediation of cell transformation by SHP2 is a complex process that involves modulation of the Ras-ERK and PI3K-Akt signaling pathways, intercellular adhesion, focal adhesion and actin cytoskeletal reorganization. To our knowledge, this is the first report showing regulation of alpha-catenin function by Tyr phosphorylation and its inhibitory effect on cell transformation.
authors.affiliation: Department of Biochemistry and Molecular Pharmacology, Robert C Byrd Health Sciences Center, West Virginia University, Morgantown, WV 26506-9142, USA.
authors.forename: J
authors.initials: J
authors.lastname: Burks
authors.forename: Y M
authors.initials: YM
authors.lastname: Agazie
mesh_terms: D000818:Animals; D002448:Cell Adhesion / Q000502:physiology; D002471:Cell Transformation, Neoplastic / Q000378:metabolism*; D015151:Immunoblotting; D047468:Immunoprecipitation; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D051379:Mice; D008856:Microscopy, Fluorescence; D041681:NIH 3T3 Cells; D010766:Phosphorylation; D021381:Protein Transport / Q000502:physiology; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism*; D051498:Receptor, Fibroblast Growth Factor, Type 3 / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism*; D051178:alpha Catenin / Q000378:metabolism*
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D051178:alpha Catenin; D014443:Tyrosine; C496366:Fgfr3 protein, mouse; D051498:Receptor, Fibroblast Growth Factor, Type 3; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D017027:Protein Tyrosine Phosphatases; C516725:Ptpn11 protein, mouse