title: The low density lipoprotein receptor-related protein 6 interacts with glycogen synthase kinase 3 and attenuates activity.
abstract: Glycogen synthase kinase 3 (GSK3) is a widely expressed Ser/Thr protein kinase that phosphorylates numerous substrates. This large number of substrates requires precise and specific regulation of GSK3 activity, which is achieved by a combination of phosphorylation, localization, and interactions with GSK3-binding proteins. Members of the Wnt canonical pathway have been shown to influence GSK3 activity. Through a yeast two-hybrid screen, we identified the Wnt canonical pathway co-receptor protein low density lipoprotein receptor-related protein 6 (LRP6) as a GSK3-binding protein. The interaction between the C terminus of LRP6 and GSK3 was also confirmed by in vitro GST pull-down assays and in situ coimmunoprecipitation assays. In vitro assays using immunoprecipitated proteins demonstrated that the C terminus of LRP6 significantly attenuated the activity of GSK3beta. In situ, LRP6 significantly decreased GSK3beta-mediated phosphorylation of tau at both primed and unprimed sites. Finally, it was also demonstrated that GSK3beta phosphorylates the PPP(S/T)P motifs in the C terminus of LRP6. This is the first identification of a direct interaction between LRP6 and GSK3, which results in an attenuation of GSK3 activity.
authors.affiliation: Department of Psychiatry, University of Alabama at Birmingham, Birmingham, Alabama 35294-0017, USA.
authors.forename: Kaihong
authors.initials: K
authors.lastname: Mi
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Dolan
authors.forename: Gail V W
authors.initials: GV
authors.lastname: Johnson
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D001665:Binding Sites; D016466:CHO Cells; D006224:Cricetinae; D005091:Exons; D015971:Gene Expression Regulation, Enzymologic; D005982:Glutathione Transferase / Q000378:metabolism; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism*; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D026502:LDL-Receptor Related Proteins / Q000378:metabolism / Q000502:physiology*; D007930:Leucine / Q000737:chemistry; D060488:Low Density Lipoprotein Receptor-Related Protein-6; D010455:Peptides / Q000737:chemistry; D010766:Phosphorylation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry; D015398:Signal Transduction; D014162:Transfection; D020798:Two-Hybrid System Techniques; D051153:Wnt Proteins / Q000378:metabolism; D016875:tau Proteins / Q000737:chemistry
chemical_list: D026502:LDL-Receptor Related Proteins; C555475:LRP6 protein, human; D060488:Low Density Lipoprotein Receptor-Related Protein-6; D010455:Peptides; D011994:Recombinant Proteins; D051153:Wnt Proteins; D016875:tau Proteins; D005982:Glutathione Transferase; D038362:Glycogen Synthase Kinase 3; D007930:Leucine