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

• Published in: Cell 2021-01, Vol.184 (1), p.194-206.e14
• Main Authors: Nygaard, Rie, Yu, Jia, Kim, Jonathan, Ross, Daniel R., Parisi, Giacomo, Clarke, Oliver B., Virshup, David M., Mancia, Filippo
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Animals; Disulfides - metabolism; Frizzled; Glycosylation; GPCR; Humans; Hydrophobic and Hydrophilic Interactions; Intracellular Signaling Peptides and Proteins - chemistry; Intracellular Signaling Peptides and Proteins - isolation & purification; Intracellular Signaling Peptides and Proteins - metabolism; membrane proteins; membrane transport; Models, Molecular; palmitoleation; 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; single-particle cryo-electron microscopy; structural biology; Structural Homology, Protein; Structure-Activity Relationship; Wnt Proteins - chemistry; Wnt Proteins - isolation & purification; Wnt Proteins - metabolism; Wnt Proteins - ultrastructure; Wnt secretion; Wnt signaling; Wntless
• ISSN: 0092-8674; 1097-4172
• DOI: 10.1016/j.cell.2020.11.038

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. [Display omitted] •We present the cryo-EM structure of human WNT8A in complex with its transporter WLS•The WLS membrane domain has structural homology to GPCRs•WLS harbors the Wnt palmitoleate in a hydrophobic cavity in its membrane domain•A conformational switch on Wnt hairpin 3 might favor unidirectional Wnt transfer The cryo-EM structure of palmitoleated human WNT8A bound to its transporter Wntless/WLS/Evi uncovers the mechanisms of Wnt secretion, revealing broad structural similarities to GPCRs and lipid-sensing pathways.