title: Phosphorylation of beta-catenin by cyclic AMP-dependent protein kinase stabilizes beta-catenin through inhibition of its ubiquitination.
abstract: The mechanism of cross talk between the Wnt signaling and cyclic AMP (cAMP)-dependent protein kinase (protein kinase A [PKA]) pathways was studied. Prostaglandin E(1) (PGE(1)), isoproterenol, and dibutyryl cAMP (Bt(2)cAMP), all of which activate PKA, increased the cytoplasmic and nuclear beta-catenin protein level, and these actions were suppressed by a PKA inhibitor and RNA interference for PKA. PGE(1) and Bt(2)cAMP also increased T-cell factor (Tcf)-dependent transcription through beta-catenin. Bt(2)cAMP suppressed degradation of beta-catenin at the protein level. Although PKA did not affect the formation of a complex between glycogen synthase kinase 3beta (GSK-3beta), beta-catenin, and Axin, phosphorylation of beta-catenin by PKA inhibited ubiquitination of beta-catenin in intact cells and in vitro. Ser675 was found to be a site for phosphorylation by PKA, and substitution of this serine residue with alanine in beta-catenin attenuated inhibition of the ubiquitination of beta-catenin by PKA, PKA-induced stabilization of beta-catenin, and PKA-dependent activation of Tcf. These results indicate that PKA inhibits the ubiquitination of beta-catenin by phosphorylating beta-catenin, thereby causing beta-catenin to accumulate and the Wnt signaling pathway to be activated.
authors.affiliation: Department of Biochemistry, Graduate School of Biomedical Sciences, Hiroshima University, Japan.
authors.forename: Shin-ichiro
authors.initials: S
authors.lastname: Hino
authors.forename: Chie
authors.initials: C
authors.lastname: Tanji
authors.forename: Keiichi I
authors.initials: KI
authors.lastname: Nakayama
authors.forename: Akira
authors.initials: A
authors.lastname: Kikuchi
mesh_terms: D000527:Alprostadil / Q000494:pharmacology; D000818:Animals; D060466:Axin Protein; D001483:Base Sequence; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D001665:Binding Sites; D003994:Bucladesine / Q000494:pharmacology; D019556:COS Cells; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D002522:Chlorocebus aethiops; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D004355:Drug Stability; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D007739:L Cells; D051379:Mice; D016297:Mutagenesis, Site-Directed; D009419:Nerve Tissue Proteins / Q000378:metabolism; D010766:Phosphorylation; D034622:RNA Interference; D012097:Repressor Proteins / Q000378:metabolism; D012694:Serine / Q000737:chemistry; D015398:Signal Transduction; D051820:TCF Transcription Factors / Q000378:metabolism; D000073940:Transcription Factor 4; D025801:Ubiquitin / Q000378:metabolism
chemical_list: D060466:Axin Protein; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D009419:Nerve Tissue Proteins; D012097:Repressor Proteins; D051820:TCF Transcription Factors; C090743:Tcf4 protein, mouse; D000073940:Transcription Factor 4; D025801:Ubiquitin; D012694:Serine; D003994:Bucladesine; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; C000605507:Gsk3b protein, mouse; D017868:Cyclic AMP-Dependent Protein Kinases; D038362:Glycogen Synthase Kinase 3; D000527:Alprostadil; D007545:Isoproterenol