Surrogate Wnt agonists that phenocopy canonical Wnt and β-catenin signalling

Nature. 2017 May 11;545(7653):234-237. doi: 10.1038/nature22306. Epub 2017 May 3.

Abstract

Wnt proteins modulate cell proliferation and differentiation and the self-renewal of stem cells by inducing β-catenin-dependent signalling through the Wnt receptor frizzled (FZD) and the co-receptors LRP5 and LRP6 to regulate cell fate decisions and the growth and repair of several tissues. The 19 mammalian Wnt proteins are cross-reactive with the 10 FZD receptors, and this has complicated the attribution of distinct biological functions to specific FZD and Wnt subtype interactions. Furthermore, Wnt proteins are modified post-translationally by palmitoylation, which is essential for their secretion, function and interaction with FZD receptors. As a result of their acylation, Wnt proteins are very hydrophobic and require detergents for purification, which presents major obstacles to the preparation and application of recombinant Wnt proteins. This hydrophobicity has hindered the determination of the molecular mechanisms of Wnt signalling activation and the functional importance of FZD subtypes, and the use of Wnt proteins as therapeutic agents. Here we develop surrogate Wnt agonists, water-soluble FZD-LRP5/LRP6 heterodimerizers, with FZD5/FZD8-specific and broadly FZD-reactive binding domains. Similar to WNT3A, these Wnt agonists elicit a characteristic β-catenin signalling response in a FZD-selective fashion, enhance the osteogenic lineage commitment of primary mouse and human mesenchymal stem cells, and support the growth of a broad range of primary human organoid cultures. In addition, the surrogates can be systemically expressed and exhibit Wnt activity in vivo in the mouse liver, regulating metabolic liver zonation and promoting hepatocyte proliferation, resulting in hepatomegaly. These surrogates demonstrate that canonical Wnt signalling can be activated by bi-specific ligands that induce receptor heterodimerization. Furthermore, these easily produced, non-lipidated Wnt surrogate agonists facilitate functional studies of Wnt signalling and the exploration of Wnt agonists for translational applications in regenerative medicine.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Differentiation
  • Cell Lineage
  • Cell Proliferation
  • Frizzled Receptors / metabolism
  • HEK293 Cells
  • Hepatocytes / cytology
  • Hepatomegaly / metabolism
  • Hepatomegaly / pathology
  • Humans
  • Hydrophobic and Hydrophilic Interactions
  • Intestines / cytology
  • Ligands
  • Liver / metabolism
  • Liver / pathology
  • Low Density Lipoprotein Receptor-Related Protein-5 / metabolism
  • Low Density Lipoprotein Receptor-Related Protein-6 / metabolism
  • Mesenchymal Stem Cells / cytology
  • Mesenchymal Stem Cells / metabolism
  • Mice
  • Models, Molecular
  • Organoids / cytology
  • Organoids / metabolism
  • Protein Multimerization
  • Signal Transduction*
  • Solubility
  • Tissue Culture Techniques
  • Wnt Proteins / agonists*
  • Wnt Proteins / metabolism*
  • Wnt Signaling Pathway*
  • beta Catenin / metabolism*

Substances

  • Frizzled Receptors
  • Ligands
  • Low Density Lipoprotein Receptor-Related Protein-5
  • Low Density Lipoprotein Receptor-Related Protein-6
  • Wnt Proteins
  • beta Catenin