R-spondins engage heparan sulfate proteoglycans to potentiate WNT signaling

Elife. 2020 May 20;9:e54469. doi: 10.7554/eLife.54469.

Abstract

R-spondins (RSPOs) amplify WNT signaling during development and regenerative responses. We previously demonstrated that RSPOs 2 and 3 potentiate WNT/β-catenin signaling in cells lacking leucine-rich repeat-containing G-protein coupled receptors (LGRs) 4, 5 and 6 (Lebensohn and Rohatgi, 2018). We now show that heparan sulfate proteoglycans (HSPGs) act as alternative co-receptors for RSPO3 using a combination of ligand mutagenesis and ligand engineering. Mutations in RSPO3 residues predicted to contact HSPGs impair its signaling capacity. Conversely, the HSPG-binding domains of RSPO3 can be entirely replaced with an antibody that recognizes heparan sulfate (HS) chains attached to multiple HSPGs without diminishing WNT-potentiating activity in cultured cells and intestinal organoids. A genome-wide screen for mediators of RSPO3 signaling in cells lacking LGRs 4, 5 and 6 failed to reveal other receptors. We conclude that HSPGs are RSPO co-receptors that potentiate WNT signaling in the presence and absence of LGRs.

Keywords: LGR; R-spondin; WNT; cell biology; development; developmental biology; heparan sulfate proteoglycans; human; single chain antibody.

Publication types

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

MeSH terms

  • Cells, Cultured
  • Developmental Biology
  • Heparan Sulfate Proteoglycans / genetics
  • Heparan Sulfate Proteoglycans / metabolism*
  • Humans
  • Intercellular Signaling Peptides and Proteins / genetics
  • Intercellular Signaling Peptides and Proteins / metabolism*
  • Ligands
  • Organoids
  • Receptors, G-Protein-Coupled / genetics
  • Receptors, G-Protein-Coupled / metabolism*
  • Thrombospondins
  • Wnt Signaling Pathway*

Substances

  • Heparan Sulfate Proteoglycans
  • Intercellular Signaling Peptides and Proteins
  • Ligands
  • RSPO3 protein, human
  • Receptors, G-Protein-Coupled
  • Rspo2 protein, human
  • Thrombospondins