Reconstitution of the destruction complex defines roles of AXIN polymers and APC in β-catenin capture, phosphorylation, and ubiquitylation

Mol Cell. 2021 Aug 19;81(16):3246-3261.e11. doi: 10.1016/j.molcel.2021.07.013. Epub 2021 Aug 4.


The Wnt/β-catenin pathway is a highly conserved, frequently mutated developmental and cancer pathway. Its output is defined mainly by β-catenin's phosphorylation- and ubiquitylation-dependent proteasomal degradation, initiated by the multi-protein β-catenin destruction complex. The precise mechanisms underlying destruction complex function have remained unknown, largely because of the lack of suitable in vitro systems. Here we describe the in vitro reconstitution of an active human β-catenin destruction complex from purified components, recapitulating complex assembly, β-catenin modification, and degradation. We reveal that AXIN1 polymerization and APC promote β-catenin capture, phosphorylation, and ubiquitylation. APC facilitates β-catenin's flux through the complex by limiting ubiquitylation processivity and directly interacts with the SCFβ-TrCP E3 ligase complex in a β-TrCP-dependent manner. Oncogenic APC truncation variants, although part of the complex, are functionally impaired. Nonetheless, even the most severely truncated APC variant promotes β-catenin recruitment. These findings exemplify the power of biochemical reconstitution to interrogate the molecular mechanisms of Wnt/β-catenin signaling.

Keywords: SCF(β-TrCP); Wnt/beta-catenin signalling; adenomatous polyposis coli (APC); axis inhibition protein (AXIN); beta-catenin destruction complex; biochemistry; casein kinase 1 (CK1); colorectal cancer; glycogen synthase kinase 3 (GSK3); ubiquitin.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenomatous Polyposis Coli Protein / genetics*
  • Adenomatous Polyposis Coli Protein / ultrastructure
  • Axin Protein / chemistry
  • Axin Protein / genetics*
  • Axin Protein / ultrastructure
  • Humans
  • Multiprotein Complexes / genetics
  • Multiprotein Complexes / ultrastructure
  • Phosphorylation / genetics
  • Protein Multimerization / genetics
  • Proteolysis
  • Ubiquitination / genetics
  • Wnt Signaling Pathway
  • beta Catenin / genetics*


  • APC protein, human
  • AXIN1 protein, human
  • Adenomatous Polyposis Coli Protein
  • Axin Protein
  • CTNNB1 protein, human
  • Multiprotein Complexes
  • beta Catenin