title: The mechanism of endogenous receptor activation functionally distinguishes prototype canonical and noncanonical Wnts.
abstract: Wnt glycoproteins are developmentally essential signaling molecules, and lesions afflicting Wnt pathways play important roles in human diseases. Some Wnts signal to the canonical pathway by stabilizing beta-catenin, while others lack this activity. Frizzled serpentine receptors mediate distinct signaling pathways by both classes of Wnts. Here, we tandemly linked noncanonical Wnt5a with the C-terminal half of Dickkopf-2 (Dkk2C), a distinct ligand of the Wnt coreceptor LRP5/6. Whereas Wnt5a, Dkk2C, or both together were incapable of stimulating endogenous canonical signaling, the Wnt5a/Dkk2C chimera efficiently activated this pathway in a manner inhibitable by specific antagonists of either frizzled or LRP receptors. Thus, activation of the canonical pathway requires ligand coupling of an endogenous frizzled/LRP coreceptor complex, rather than Wnt triggering each receptor independently. Moreover, fusion of Wnt5a with Dkk2C unmasked its ability to signal to Dishevelled through multiple frizzleds, indicating that the lack of functional interaction with LRP distinguishes noncanonical Wnt5a from canonical Wnts in mammalian cells. These findings provide a novel mechanism by which the same receptor can be switched between distinct signaling pathways depending on the differential recruitment of a coreceptor by members of the same ligand family.
authors.affiliation: Department of Oncological Sciences, Mount Sinai School of Medicine, Box 1130, One Gustave L. Levy Place, New York, NY 10029, USA.
authors.forename: Guizhong
authors.initials: G
authors.lastname: Liu
authors.forename: Anna
authors.initials: A
authors.lastname: Bafico
authors.forename: Stuart A
authors.initials: SA
authors.lastname: Aaronson
mesh_terms: D000818:Animals; D002460:Cell Line; D003598:Cytoskeletal Proteins / Q000378:metabolism; D051157:Frizzled Receptors; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000502:physiology*; D026502:LDL-Receptor Related Proteins; D008024:Ligands; D060492:Low Density Lipoprotein Receptor-Related Protein-5; D051379:Mice; D011506:Proteins / Q000235:genetics / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000502:physiology*; D011973:Receptors, LDL / Q000235:genetics / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000502:physiology; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology; D015534:Trans-Activators / Q000378:metabolism; D051153:Wnt Proteins; D000071818:Wnt-5a Protein; D060508:Wnt3 Protein; D051176:beta Catenin
chemical_list: C495270:CTNNB1 protein, human; C495267:CTNNB1 protein, mouse; D003598:Cytoskeletal Proteins; C498622:DKK2 protein, human; C405060:Dkk2 protein, mouse; D051157:Frizzled Receptors; D036341:Intercellular Signaling Peptides and Proteins; D026502:LDL-Receptor Related Proteins; C555482:LRP5 protein, human; D008024:Ligands; D060492:Low Density Lipoprotein Receptor-Related Protein-5; C555483:Lrp5 protein, mouse; D011506:Proteins; D011518:Proto-Oncogene Proteins; D011973:Receptors, LDL; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D051153:Wnt Proteins; D000071818:Wnt-5a Protein; D060508:Wnt3 Protein; C438615:Wnt5a protein, mouse; D051176:beta Catenin