title: Inhibitory phosphorylation of glycogen synthase kinase-3 (GSK-3) in response to lithium. Evidence for autoregulation of GSK-3.
abstract: Glycogen synthase kinase-3 (GSK-3) is a critical, negative regulator of diverse signaling pathways. Lithium is a direct inhibitor of GSK-3 and has been widely used to test the putative role of GSK-3 in multiple settings. However, lithium also inhibits other targets, including inositol monophosphatase and structurally related phosphomonoesterases, and thus additional approaches are needed to attribute a given biological effect of lithium to a specific target. For example, lithium is known to increase the inhibitory N-terminal phosphorylation of GSK-3, but the target of lithium responsible for this indirect regulation has not been identified. We have characterized a short peptide derived from the GSK-3 interaction domain of Axin that potently inhibits GSK-3 activity in vitro and in mammalian cells and robustly activates Wnt-dependent transcription, mimicking lithium action. We show here, using the GSK-3 interaction domain peptide, as well as small molecule inhibitors of GSK-3, that lithium induces GSK-3 N-terminal phosphorylation through direct inhibition of GSK-3 itself. Reduction of GSK-3 protein levels, either by RNA interference or by disruption of the mouse GSK-3beta gene, causes increased N-terminal phosphorylation of GSK-3, confirming that GSK-3 regulates its own phosphorylation status. Finally, evidence is presented that N-terminal phosphorylation of GSK-3 can be regulated by the GSK-3-dependent protein phosphatase-1.inhibitor-2 complex.
authors.affiliation: Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6148, USA.
authors.forename: Fang
authors.initials: F
authors.lastname: Zhang
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Phiel
authors.forename: Laura
authors.initials: L
authors.lastname: Spece
authors.forename: Nadia
authors.initials: N
authors.lastname: Gurvich
authors.forename: Peter S
authors.initials: PS
authors.lastname: Klein
mesh_terms: D016475:3T3 Cells; D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D015971:Gene Expression Regulation, Enzymologic; D017930:Genes, Reporter; D038362:Glycogen Synthase Kinase 3 / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D015151:Immunoblotting; D020128:Inhibitory Concentration 50; D008094:Lithium / Q000494:pharmacology*; D051379:Mice; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D010455:Peptides / Q000737:chemistry; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D054645:Protein Phosphatase 1; D017434:Protein Structure, Tertiary; D034622:RNA Interference; D011994:Recombinant Proteins / Q000378:metabolism; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism; D038744:Ribosomal Protein S6 Kinases, 90-kDa / Q000378:metabolism; D012694:Serine / Q000737:chemistry; D014158:Transcription, Genetic; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D010455:Peptides; D011994:Recombinant Proteins; D012694:Serine; D008094:Lithium; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D038744:Ribosomal Protein S6 Kinases, 90-kDa; C069330:ribosomal protein S6 kinase, 90kDa, polypeptide 3; D017868:Cyclic AMP-Dependent Protein Kinases; D038362:Glycogen Synthase Kinase 3; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1