Cell signaling · Development
The same Wnt protein switches β-catenin signaling on or off, depending on the receptor
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Short answer
Purified Wnt5a activates or inhibits β-catenin–TCF signaling depending on which receptors the responding cell expresses.
What happened
Mikels and Nusse purified Wnt5a protein rather than relying on overexpression, then applied it across defined receptor contexts. With an appropriate Frizzled receptor present, Wnt5a drove canonical β-catenin–TCF signaling. Without it, the same purified protein inhibited that pathway.
Why it matters
Wnt5a had been reported as canonical in some papers and as an antagonist in others, and the field treated the disagreement as a controversy about the ligand. This reframes it as a controversy about the assay: the cells, not the protein, were the variable.
Evidence
- Study type
- Purified-ligand signaling assays across defined receptor contexts
- Sample
- Cell-based receptor-context assays; no single sample N
- Journal
- PLoS Biology · peer reviewed
- Replication
- Not assessed in this corpus; context-dependence is now the standard reading of the Wnt5a literature
- Limitations
- One purified ligand in engineered receptor contexts. It does not establish which receptor combinations dominate in any particular tissue.
What this connects to
Sources
The one study this explanation is built from, by the role each plays. Every source links to PaperFren’s explanation of it and to the original paper.
Primary study
- When does Wnt5a turn β-catenin signaling on or off?
Purified Wnt5a can activate or inhibit β-catenin–TCF signaling depending on which Frizzled/receptor context is present.
What it does not showLimitations
One purified ligand study does not map every tissue’s endogenous receptor set.
PaperFren explanationStudy with cards and a quizOriginal paper (DOI)cc by
Before
Wnts were sorted into canonical and noncanonical classes as a property of the ligand, and conflicting Wnt5a reports were read as contradictions.
Now
Ligand class is a property of the ligand-receptor pair. This resolves the specific Wnt5a conflict; it does not map which receptors are actually present in any given tissue, which is what would be needed to predict the output in vivo.