Structure-function analysis of secreted frizzled-related protein-1 for its Wnt antagonist function

J Cell Biochem. 2007 Dec 15;102(6):1519-28. doi: 10.1002/jcb.21372.


Secreted frizzled-related proteins (sFRPs) are glycoproteins that are recognized as Wnt antagonists. To identify the functional domains that are involved in Wnt antagonist function, several sFRP-1 mutants and sFRP-1/sFRP-2 chimeras were generated. These mutants were characterized in an optimized T-cell factor (TCF)-luciferase based assay in U2OS human osteosarcoma cells. Deletions of the sFRP-1 cysteine rich domain (CRD) lead to the complete loss of Wnt antagonist function. A region between amino acids 73-86 within the second loop of the CRD of sFRP-1 was necessary for the optimal Wnt inhibitory function. Within this region, a conserved tyrosine residue played a critical role, and its change to neutral or polar amino acids lead to decreased Wnt inhibitory activity. The sFRP-1/sFRP-2 chimeras with the netrin domain of sFRP-1 replaced by corresponding sFRP-2 sequences showed 40-70% loss of Wnt antagonist function. The sFRP-1/sFRP-2 chimera with the replacement of C-terminal 19 amino acids of sFRP-1 with 11 amino acids of sFRP-2 resulted in 70% loss of activity indicating that carboxyl-terminal region of sFRP-1 is important for its Wnt inhibitory activity. The structure-function analysis studies of sFRP-1 clearly demonstrate the interaction of several functional domains for its optimal Wnt antagonist function.

MeSH terms

  • Amino Acid Sequence
  • Amino Acid Substitution
  • Cell Line, Tumor
  • Conserved Sequence
  • Gene Deletion
  • Genes, Reporter
  • Humans
  • Intercellular Signaling Peptides and Proteins / chemistry*
  • Intercellular Signaling Peptides and Proteins / genetics
  • Luciferases / metabolism
  • Membrane Proteins / chemistry*
  • Membrane Proteins / genetics
  • Molecular Sequence Data
  • Mutant Chimeric Proteins / metabolism
  • Osteosarcoma / pathology
  • Plasmids
  • Protein Binding
  • Protein Structure, Secondary
  • Protein Structure, Tertiary
  • Sequence Homology, Amino Acid
  • Structure-Activity Relationship*
  • Transfection
  • Tryptophan / chemistry
  • Tyrosine / chemistry
  • Wnt Proteins / antagonists & inhibitors*


  • Intercellular Signaling Peptides and Proteins
  • Membrane Proteins
  • Mutant Chimeric Proteins
  • SFRP1 protein, human
  • Wnt Proteins
  • Tyrosine
  • Tryptophan
  • Luciferases