Active and water-soluble form of lipidated Wnt protein is maintained by a serum glycoprotein afamin/α-albumin

Elife. 2016 Feb 23;5:e11621. doi: 10.7554/eLife.11621.

Abstract

Wnt plays important role during development and in various diseases. Because Wnts are lipidated and highly hydrophobic, they can only be purified in the presence of detergents, limiting their use in various in vitro and in vivo assays. We purified N-terminally tagged recombinant Wnt3a secreted from cells and accidentally discovered that Wnt3a co-purified with a glycoprotein afamin derived from the bovine serum included in the media. Wnt3a forms a 1:1 complex with afamin, which remains soluble in aqueous buffer after isolation, and can induce signaling in various cellular systems including the intestical stem cell growth assay. By co-expressing with afamin, biologically active afamin-Wnt complex can be easily obtained in large quantity. As afamin can also solubilize Wnt5a, Wnt3, and many more Wnt subtypes, afamin complexation will open a way to put various Wnt ligands and their signaling mechanisms under a thorough biochemical scrutiny that had been difficult for years.

Keywords: afamin; biochemistry; developmental biology; epitope tag; human; lipid modification; mouse; purification; serum; stem cells; wnt.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Carrier Proteins / chemistry
  • Carrier Proteins / metabolism*
  • Cattle
  • Glycoproteins / chemistry
  • Glycoproteins / metabolism*
  • Hydrophobic and Hydrophilic Interactions
  • Protein Binding
  • Serum Albumin / chemistry
  • Serum Albumin / metabolism*
  • Solubility
  • Water
  • Wnt Proteins / chemistry
  • Wnt Proteins / metabolism*

Substances

  • Carrier Proteins
  • Glycoproteins
  • Serum Albumin
  • Wnt Proteins
  • Water

Grant support

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.