Structural Basis of WLS/Evi-Mediated Wnt Transport and Secretion

Cell. 2021 Jan 7;184(1):194-206.e14. doi: 10.1016/j.cell.2020.11.038. Epub 2020 Dec 23.


Wnts are evolutionarily conserved ligands that signal at short range to regulate morphogenesis, cell fate, and stem cell renewal. The first and essential steps in Wnt secretion are their O-palmitoleation and subsequent loading onto the dedicated transporter Wntless/evenness interrupted (WLS/Evi). We report the 3.2 Å resolution cryogenic electron microscopy (cryo-EM) structure of palmitoleated human WNT8A in complex with WLS. This is accompanied by biochemical experiments to probe the physiological implications of the observed association. The WLS membrane domain has close structural homology to G protein-coupled receptors (GPCRs). A Wnt hairpin inserts into a conserved hydrophobic cavity in the GPCR-like domain, and the palmitoleate protrudes between two helices into the bilayer. A conformational switch of highly conserved residues on a separate Wnt hairpin might contribute to its transfer to receiving cells. This work provides molecular-level insights into a central mechanism in animal body plan development and stem cell biology.

Keywords: Frizzled; GPCR; Wnt secretion; Wnt signaling; Wntless; membrane proteins; membrane transport; palmitoleation; single-particle cryo-electron microscopy; structural biology.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Disulfides / metabolism
  • Glycosylation
  • Humans
  • Hydrophobic and Hydrophilic Interactions
  • Intracellular Signaling Peptides and Proteins / chemistry*
  • Intracellular Signaling Peptides and Proteins / isolation & purification
  • Intracellular Signaling Peptides and Proteins / metabolism*
  • Models, Molecular
  • Protein Binding
  • Protein Domains
  • Protein Structure, Secondary
  • Protein Transport
  • Receptors, G-Protein-Coupled / chemistry*
  • Receptors, G-Protein-Coupled / isolation & purification
  • Receptors, G-Protein-Coupled / metabolism*
  • Receptors, G-Protein-Coupled / ultrastructure
  • Structural Homology, Protein
  • Structure-Activity Relationship
  • Wnt Proteins / chemistry
  • Wnt Proteins / isolation & purification
  • Wnt Proteins / metabolism*
  • Wnt Proteins / ultrastructure


  • Disulfides
  • Intracellular Signaling Peptides and Proteins
  • Receptors, G-Protein-Coupled
  • WLS protein, human
  • WNT8A protein, human
  • Wnt Proteins