title: Beyond Wnt inhibition: new functions of secreted Frizzled-related proteins in development and disease.
abstract: The secreted Frizzled-related proteins (SFRPs) are a family of soluble proteins that are structurally related to Frizzled (Fz) proteins, the serpentine receptors that mediate the extensively used cell-cell communication pathway involving Wnt signalling. Because of their homology with the Wnt-binding domain on the Fz receptors, SFRPs were immediately characterised as antagonists that bind to Wnt proteins to prevent signal activation. Since these initial studies, interest in the family of SFRPs has grown progressively, offering new perspectives on their function and mechanism of action in both development and disease. These studies indicate that SFRPs are not merely Wnt-binding proteins, but can also antagonise one another's activity, bind to Fz receptors and influence axon guidance, interfere with BMP signalling by acting as proteinase inhibitors, and interact with other receptors or matrix molecules. Furthermore, their expression is altered in different types of cancers, bone pathologies, retinal degeneration and hypophosphatemic diseases, indicating that their activity is fundamental for tissue homeostasis. Here we review some of the debated aspects of SFRP-Wnt interactions and discuss the new and emerging roles of SFRPs.
authors.affiliation: Departamento de Neurobiología Molecular, Celular y del Desarrollo, Instituto Cajal, CSIC, Dr Arce 37, Madrid 28002, Spain. bovolenta@cajal.csic.es
authors.forename: Paola
authors.initials: P
authors.lastname: Bovolenta
authors.forename: Pilar
authors.initials: P
authors.lastname: Esteve
authors.forename: Jose Maria
authors.initials: JM
authors.lastname: Ruiz
authors.forename: Elsa
authors.initials: E
authors.lastname: Cisneros
authors.forename: Javier
authors.initials: J
authors.lastname: Lopez-Rios
mesh_terms: D000818:Animals; D051157:Frizzled Receptors / Q000378:metabolism; D006023:Glycoproteins / Q000737:chemistry / Q000145:classification / Q000502:physiology*; D048788:Growth and Development; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D009369:Neoplasms / Q000378:metabolism; D015398:Signal Transduction; D051153:Wnt Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D000099274:Frizzled-Related Proteins
chemical_list: D051157:Frizzled Receptors; D006023:Glycoproteins; D047908:Intracellular Signaling Peptides and Proteins; D051153:Wnt Proteins; D000099274:Frizzled-Related Proteins