Novel Peptides that Block the Interaction between Wnt and Frizzled

Abstract

IntroductionWnt/Frizzled signaling is involved in many developmental processes but is mostly silent in healthy adult organs. However, a reactivation of this signaling pathway is generally observed during pathological conditions, which makes it a promising therapeutic target. The recently presented crystal structure of Xenopus Wnt8 in complex with the cysteine rich domain (CRD) of Frizzled8 demonstrates that Wnt has a shape resembling the outline of a hand with a thumb and index finger grasping the CRD at two opposing sites. The thumb contains a palmitic acid lipid at the tip that engages a groove on the CRD whereas the index finger forms a strong hydrophobic contact with a groove on the opposite side of the CRD. Here we investigated the antagonistic properties of peptides that resemble fragments of Wnts that interact with the CRD of Frizzled receptors on canonical Wnt/Frizzled signaling in cell‐based assays.MethodsPeptides resembling the thumb and index finger of Wnt3a and Wnt5a were synthesized and tested in HEK293 and 3T3 cells expressing the TOPFlash reporter. Canonical Wnt signaling was induced by addition of Wnt3a conditioned medium.ResultsPeptide fragments of both thumb and index finger demonstrated inhibition of Wnt3a induced signaling in micromolar concentrations. Combined administration of both fragments demonstrated an additive inhibition. Furthermore, we demonstrated that palmitoylation, tertiary structure and length of the peptide are critical for antagonistic activity.ConclusionFragments of Wnt that interact with Frizzled CRDs can serve as new antagonists for Wnt/Frizzled signaling.Supported by the Dutch Heart Foundation (2010B196) and Cyttron (FES0908)