title: Regulation of beta-catenin signaling by the B56 subunit of protein phosphatase 2A.
abstract: Dysregulation of Wnt-beta-catenin signaling disrupts axis formation in vertebrate embryos and underlies multiple human malignancies. The adenomatous polyposis coli (APC) protein, axin, and glycogen synthase kinase 3beta form a Wnt-regulated signaling complex that mediates the phosphorylation-dependent degradation of beta-catenin. A protein phosphatase 2A (PP2A) regulatory subunit, B56, interacted with APC in the yeast two-hybrid system. Expression of B56 reduced the abundance of beta-catenin and inhibited transcription of beta-catenin target genes in mammalian cells and Xenopus embryo explants. The B56-dependent decrease in beta-catenin was blocked by oncogenic mutations in beta-catenin or APC, and by proteasome inhibitors. B56 may direct PP2A to dephosphorylate specific components of the APC-dependent signaling complex and thereby inhibit Wnt signaling.
authors: Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah, Salt Lake City, UT 84132, USA.
authors: J M
authors: JM
authors: Seeling
authors: J R
authors: JR
authors: Miller
authors: R
authors: R
authors: Gil
authors: R T
authors: RT
authors: Moon
authors: R
authors: R
authors: White
authors: D M
authors: DM
authors: Virshup
mesh_terms: D025601:Adenomatous Polyposis Coli Protein; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002460:Cell Line; D003546:Cysteine Endopeptidases / Q000378:metabolism; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation; D017930:Genes, Reporter; D038362:Glycogen Synthase Kinase 3; D038341:Glycogen Synthase Kinases; D006801:Humans; D007976:Leupeptins / Q000494:pharmacology; D009097:Multienzyme Complexes / Q000378:metabolism; D009154:Mutation; D010749:Phosphoprotein Phosphatases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex; D054648:Protein Phosphatase 2; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D015398:Signal Transduction; D015534:Trans-Activators; D015533:Transcriptional Activation; D014162:Transfection; D014407:Tumor Cells, Cultured; D051153:Wnt Proteins; D014981:Xenopus; D029867:Xenopus Proteins; D029961:Zebrafish Proteins; D051176:beta Catenin
chemical_list: D025601:Adenomatous Polyposis Coli Protein; C495266:CTNNB1 protein, Xenopus; C495270:CTNNB1 protein, human; D015853:Cysteine Proteinase Inhibitors; D003598:Cytoskeletal Proteins; D007976:Leupeptins; D009097:Multienzyme Complexes; D011518:Proto-Oncogene Proteins; D015534:Trans-Activators; D051153:Wnt Proteins; D029867:Xenopus Proteins; D029961:Zebrafish Proteins; D051176:beta Catenin; C063261:acetylleucyl-leucyl-norleucinal; D038341:Glycogen Synthase Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D038362:Glycogen Synthase Kinase 3; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde