title: Pathway specificity by the bifunctional receptor frizzled is determined by affinity for wingless.
abstract: The Frizzled (Fz) protein in Drosophila is a bifunctional receptor that acts through a GTPase pathway in planar polarity signaling and as a receptor for Wingless (Wg) using the canonical Wnt pathway. We found that the ligand-binding domain (CRD) of Fz has an approximately 10-fold lower affinity for Wg than the CRD of DFz2, a Wg receptor without polarity activity. When the Fz CRD is replaced by the high-affinity CRD of DFz2, the resulting chimeric protein gains Wg signaling activity, yet also retains polarity signaling activity. In contrast, the reciprocal exchange of the Fz CRD onto DFz2 is not sufficient to confer polarity activity to DFz2. This suggests that Fz has an intrinsic capacity for polarity signaling and that high-affinity interaction with Wg couples it to the Wnt pathway.
authors.affiliation: Howard Hughes Medical Institute and Department of Developmental Biology, Stanford University, California 94305, USA.
authors.forename: E J
authors.initials: EJ
authors.lastname: Rulifson
authors.forename: C H
authors.initials: CH
authors.lastname: Wu
authors.forename: R
authors.initials: R
authors.lastname: Nusse
mesh_terms: D000818:Animals; D004330:Drosophila / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D029721:Drosophila Proteins; D005260:Female; D051157:Frizzled Receptors; D017344:Genes, Insect; D019476:Insect Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008024:Ligands; D008297:Male; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D043562:Receptors, G-Protein-Coupled; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D014921:Wings, Animal / Q000254:growth & development; D051155:Wnt1 Protein
chemical_list: D029721:Drosophila Proteins; D051157:Frizzled Receptors; D019476:Insect Proteins; D008024:Ligands; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D011993:Recombinant Fusion Proteins; D051155:Wnt1 Protein; C058784:fz protein, Drosophila; C074622:wg protein, Drosophila