title: Regulation of glycogen synthase kinase 3beta and downstream Wnt signaling by axin.
abstract: Axin is a recently identified protein encoded by the fused locus in mice that is required for normal vertebrate axis formation. We have defined a 25-amino-acid sequence in axin that comprises the glycogen synthase kinase 3beta (GSK-3beta) interaction domain (GID). In contrast to full-length axin, which has been shown to antagonize Wnt signaling, the GID inhibits GSK-3beta in vivo and activates Wnt signaling. Similarly, mutants of axin lacking key regulatory domains such as the RGS domain, which is required for interaction with the adenomatous polyposis coli protein, bind and inhibit GSK-3beta in vivo, suggesting that these domains are critical for proper regulation of GSK-3beta activity. We have identified a novel self-interaction domain in axin and have shown that formation of an axin regulatory complex in vivo is critical for axis formation and GSK-3beta activity. Based on these data, we propose that the axin complex may directly regulate GSK-3beta enzymatic activity in vivo. These observations also demonstrate that alternative inhibitors of GSK-3beta can mimic the effect of lithium in developing Xenopus embryos.
authors.affiliation: Cell and Molecular Biology Graduate Group, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6148, USA.
authors.forename: C M
authors.initials: CM
authors.lastname: Hedgepeth
authors.forename: M A
authors.initials: MA
authors.lastname: Deardorff
authors.forename: K
authors.initials: K
authors.lastname: Rankin
authors.forename: P S
authors.initials: PS
authors.lastname: Klein
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D025601:Adenomatous Polyposis Coli Protein; D000595:Amino Acid Sequence; D000818:Animals; D060466:Axin Protein; D019521:Body Patterning / Q000187:drug effects; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D038362:Glycogen Synthase Kinase 3; D038341:Glycogen Synthase Kinases; D047908:Intracellular Signaling Peptides and Proteins; D008094:Lithium / Q000494:pharmacology; D051379:Mice; D008954:Models, Biological; D018716:Molecular Mimicry; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins; D011485:Protein Binding; D011506:Proteins / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D020710:RGS Proteins / Q000378:metabolism; D012097:Repressor Proteins; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D015534:Trans-Activators; D051153:Wnt Proteins; D014981:Xenopus; D029867:Xenopus Proteins; D029961:Zebrafish Proteins; D051176:beta Catenin
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D025601:Adenomatous Polyposis Coli Protein; D060466:Axin Protein; C495266:CTNNB1 protein, Xenopus; C495267:CTNNB1 protein, mouse; D002352:Carrier Proteins; D003598:Cytoskeletal Proteins; C491818:Frat1 protein, mouse; D047908:Intracellular Signaling Peptides and Proteins; D009363:Neoplasm Proteins; C112892:PIAS1 protein, Xenopus; D011506:Proteins; D011518:Proto-Oncogene Proteins; D020710:RGS Proteins; D012097:Repressor Proteins; D015534:Trans-Activators; D051153:Wnt Proteins; D029867:Xenopus Proteins; D029961:Zebrafish Proteins; C555454:axin1 protein, Xenopus; D051176:beta Catenin; D008094:Lithium; D038341:Glycogen Synthase Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D038362:Glycogen Synthase Kinase 3