title: Functional characterization of WNT7A signaling in PC12 cells: interaction with A FZD5 x LRP6 receptor complex and modulation by Dickkopf proteins.
abstract: WNT factors represent key mediators of many processes in animal development and homeostasis and act through a receptor complex comprised of members of the Frizzled and low density lipoprotein-related receptors (LRP). In mammals, 19 genes encoding Wingless and Int-related factor (WNTs), 10 encoding Frizzled, and 2 encoding LRP proteins have been identified, but little is known of the identities of individual Frizzled-LRP combinations mediating the effects of specific WNT factors. Additionally, several secreted modulators of WNT signaling have been identified, including at least three members of the Dickkopf family. WNT7A is a WNT family member expressed in the vertebrate central nervous system capable of modulating aspects of neuronal plasticity. Gene knock-out models in the mouse have revealed that WNT7A plays a role in cerebellar maturation, although its function in the development of distal limb structures and of the reproductive tract have been more intensely studied. To identify a receptor complex for this WNT family member, we have analyzed the response of the rat pheochromocytoma cell line PC12 to WNT7A. We find that PC12 cells are capable of responding to WNT7A as measured by increased beta-catenin stability and activation of a T-cell factor-based luciferase reporter construct and that these cells express three members of the Frizzled family (Frizzled-2, -5, and -7) and LRP6. Our functional analysis indicates that WNT7A can specifically act via a Frizzled-5.LRP6 receptor complex in PC12 cells and that this activity can be antagonized by Dickkopf-1 and Dickkopf-3.
authors.affiliation: Department of Human Physiology and Pharmacology, University of Rome La Sapienza, Piazzale Aldo Moro 5, 00185 Rome, Italy. acaricasole@sienabiotech.it
authors.forename: Andrea
authors.initials: A
authors.lastname: Caricasole
authors.forename: Teresa
authors.initials: T
authors.lastname: Ferraro
authors.forename: Luisa
authors.initials: L
authors.lastname: Iacovelli
authors.forename: Eliana
authors.initials: E
authors.lastname: Barletta
authors.forename: Alessandra
authors.initials: A
authors.lastname: Caruso
authors.forename: Daniela
authors.initials: D
authors.lastname: Melchiorri
authors.forename: Georg C
authors.initials: GC
authors.lastname: Terstappen
authors.forename: Ferdinando
authors.initials: F
authors.lastname: Nicoletti
mesh_terms: D000818:Animals; D036341:Intercellular Signaling Peptides and Proteins; D060488:Low Density Lipoprotein Receptor-Related Protein-6; D016716:PC12 Cells; D011506:Proteins / Q000502:physiology*; D011518:Proto-Oncogene Proteins; D051381:Rats; D011956:Receptors, Cell Surface / Q000502:physiology*; D011973:Receptors, LDL / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*; D051153:Wnt Proteins
chemical_list: C501127:Dkk1 protein, mouse; C498626:Dkk3 protein, rat; D036341:Intercellular Signaling Peptides and Proteins; C555475:LRP6 protein, human; D060488:Low Density Lipoprotein Receptor-Related Protein-6; C555476:Lrp6 protein, mouse; C555477:Lrp6 protein, rat; D011506:Proteins; D011518:Proto-Oncogene Proteins; D011956:Receptors, Cell Surface; D011973:Receptors, LDL; D051153:Wnt Proteins; C490508:Wnt7a protein, mouse; C490507:Wnt7a protein, rat