title: Stability elements in the LRP6 cytoplasmic tail confer efficient signalling upon DIX-dependent polymerization.
abstract: Wnt/beta-catenin signalling controls cell fates in development, tissue homeostasis and cancer. Wnt binding to Frizzled receptors triggers recruitment of Dishevelled to the plasma membrane and formation of a signalosome containing the LRP5/6 co-receptor, whose cytoplasmic tail (ctail) thus becomes phosphorylated at multiple PPP(S/T)Px(S/T) motifs. These then directly inhibit GSK3beta, which results in beta-catenin accumulation and signalling. Here, we revisit previous epistasis experiments, and show that Dishevelled signals through LRP5/6 in human cells and Drosophila embryos. To recapitulate this signalling event, and to define its functional elements, we fused the Dishevelled DIX domain to the LRP6 ctail, which forms cytoplasmic signalosomes with potent signalling activity mediated by its PPP(S/T)Px(S/T) motifs. Their phosphorylation and activity depends critically on DIX-mediated polymerization, and on multiple stability elements in the LRP6 ctail, including the T1479 epitope upstream of the membrane-proximal PPP(S/T)Px(S/T) motif. Thus, stable polymerization emerges as a key principle underlying the function of Dishevelled-dependent signalosomes.
authors.affiliation: MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, UK.
authors.forename: Ciara
authors.initials: C
authors.lastname: Metcalfe
authors.forename: Carolina
authors.initials: C
authors.lastname: Mendoza-Topaz
authors.forename: Juliusz
authors.initials: J
authors.lastname: Mieszczanek
authors.forename: Mariann
authors.initials: M
authors.lastname: Bienz
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry* / Q000378:metabolism; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D060466:Axin Protein; D001704:Biopolymers / Q000378:metabolism*; D002460:Cell Line; D000072261:Dishevelled Proteins; D029721:Drosophila Proteins / Q000737:chemistry / Q000378:metabolism; D004331:Drosophila melanogaster / Q000196:embryology / Q000378:metabolism*; D004625:Embryo, Nonmammalian / Q000378:metabolism; D000939:Epitopes / Q000737:chemistry; D006801:Humans; D060488:Low Density Lipoprotein Receptor-Related Protein-6; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000737:chemistry* / Q000378:metabolism; D010766:Phosphorylation; D055550:Protein Stability; D017434:Protein Structure, Tertiary; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000378:metabolism; D011973:Receptors, LDL / Q000737:chemistry* / Q000378:metabolism*; D012097:Repressor Proteins / Q000378:metabolism; D015398:Signal Transduction; D013329:Structure-Activity Relationship; D051153:Wnt Proteins / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D060466:Axin Protein; D001704:Biopolymers; D000072261:Dishevelled Proteins; D029721:Drosophila Proteins; D000939:Epitopes; C555475:LRP6 protein, human; D060488:Low Density Lipoprotein Receptor-Related Protein-6; D010750:Phosphoproteins; D011956:Receptors, Cell Surface; D011973:Receptors, LDL; D012097:Repressor Proteins; D051153:Wnt Proteins; C474373:arr protein, Drosophila; C000606588:dsh protein, Drosophila
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