title: Glycogen Synthase Kinase 3β Is Positively Regulated by Protein Kinase Cζ-Mediated Phosphorylation Induced by Wnt Agonists.
abstract: The molecular events that drive Wnt-induced regulation of glycogen synthase kinase 3β (GSK-3β) activity are poorly defined. In this study, we found that protein kinase Cζ (PKCζ) and GSK-3β interact mainly in colon cancer cells. Wnt stimulation induced a rapid GSK-3β redistribution from the cytoplasm to the nuclei in malignant cells and a transient PKC-mediated phosphorylation of GSK-3β at a different site from serine 9. In addition, while Wnt treatment induced a decrease in PKC-mediated phosphorylation of GSK-3β in nonmalignant cells, in malignant cells, this phosphorylation was increased. Pharmacological inhibition and small interfering RNA (siRNA)-mediated silencing of PKCζ abolished all of these effects, but unexpectedly, it also abolished the constitutive basal activity of GSK-3β. In vitro activity assays demonstrated that GSK-3β phosphorylation mediated by PKCζ enhanced GSK-3β activity. We mapped Ser147 of GSK-3β as the site phosphorylated by PKCζ, i.e., its mutation into alanine abolished GSK-3β activity, resulting in β-catenin stabilization and increased transcriptional activity, whereas phosphomimetic replacement of Ser147 by glutamic acid maintained GSK-3β basal activity. Thus, we found that PKCζ phosphorylates GSK-3β at Ser147 to maintain its constitutive activity in resting cells and that Wnt stimulation modifies the phosphorylation of Ser147 to regulate GSK-3β activity in opposite manners in normal and malignant colon cells.
authors.affiliation: Department of Biochemistry, Faculty of Medicine, Universidad Nacional Autónoma de México (UNAM), Mexico City, Mexico.
authors.forename: Nydia
authors.initials: N
authors.lastname: Tejeda-Muñoz
authors.affiliation: Department of Biochemistry, Faculty of Medicine, Universidad Nacional Autónoma de México (UNAM), Mexico City, Mexico.
authors.forename: Héctor
authors.initials: H
authors.lastname: González-Aguilar
authors.affiliation: Department of Biochemistry, Faculty of Medicine, Universidad Nacional Autónoma de México (UNAM), Mexico City, Mexico.
authors.forename: Paula
authors.initials: P
authors.lastname: Santoyo-Ramos
authors.affiliation: Department of Biochemistry, Faculty of Medicine, Universidad Nacional Autónoma de México (UNAM), Mexico City, Mexico.
authors.forename: M Cristina
authors.initials: MC
authors.lastname: Castañeda-Patlán
authors.affiliation: Department of Biochemistry, Faculty of Medicine, Universidad Nacional Autónoma de México (UNAM), Mexico City, Mexico rmartha@unam.mx.
authors.forename: Martha
authors.identifier: http://orcid.org/0000-0001-6277-3170
authors.initials: M
authors.lastname: Robles-Flores
mesh_terms: D002460:Cell Line; D045744:Cell Line, Tumor; D003106:Colon / Q000378:metabolism / Q000473:pathology; D003110:Colonic Neoplasms / Q000378:metabolism / Q000473:pathology; D004789:Enzyme Activation / Q000187:drug effects; D038362:Glycogen Synthase Kinase 3 / Q000032:analysis / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000032:analysis / Q000378:metabolism*; D051153:Wnt Proteins / Q000819:agonists; D000099221:Protein Kinase C zeta
chemical_list: D038362:Glycogen Synthase Kinase 3; D000071679:Glycogen Synthase Kinase 3 beta; D011493:Protein Kinase C; D051153:Wnt Proteins; D000099221:Protein Kinase C zeta; C000605506:GSK3B protein, human