Beyond Wnt inhibition: new functions of secreted Frizzled-related proteins in development and disease

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…