Caspase cleavage of the APC tumor suppressor and release of an amino-terminal domain is required for the transcription-independent function of APC in apoptosis

Oncogene. 2007 Jul 19;26(33):4872-6. doi: 10.1038/sj.onc.1210265. Epub 2007 Feb 5.

Abstract

The adenomatous polyposis coli (APC) tumor suppressor is inactivated by mutation in most colorectal tumors. APC is a component of the Wnt signaling pathway and is best known for its ability to downregulate beta-catenin and consequent effects on transcriptional regulation. Previous work demonstrated that APC accelerates apoptosis-associated caspase activity independently of transcription, and suggested novel tumor suppressor functions of APC. In this work, we have mapped the APC apoptosis-accelerating region to amino acids (aa) 1-760 by testing a series of non-overlapping APC segments. Interestingly, this segment corresponds to a stable group II caspase cleavage product of APC released during apoptosis that includes the amino-terminal aa1-777. Mutation of the APC aspartic acid residue at position 777 to an alanine completely abolished in vitro cleavage of APC by a recombinant group II caspase and rendered the full-length protein unable to accelerate apoptosis in vitro. A truncated APC protein associated with familial and sporadic colorectal cancer, also unable to accelerate apoptosis in vitro and in vivo, is resistant to group II caspase cleavage. These results demonstrate that cleavage of APC and the subsequent release of an amino-terminal segment are necessary for the transcription-independent mechanism of APC-mediated apoptosis.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adenomatous Polyposis Coli Protein / chemistry
  • Adenomatous Polyposis Coli Protein / genetics
  • Adenomatous Polyposis Coli Protein / metabolism*
  • Apoptosis / genetics
  • Apoptosis / physiology*
  • Blotting, Western
  • Caspase 3 / genetics
  • Caspase 3 / metabolism
  • Caspases / genetics
  • Caspases / metabolism*
  • Cell Line, Tumor
  • Green Fluorescent Proteins / genetics
  • Green Fluorescent Proteins / metabolism
  • Humans
  • Luciferases / genetics
  • Luciferases / metabolism
  • Molecular Weight
  • Mutation
  • Peptide Fragments / chemistry
  • Peptide Fragments / genetics
  • Peptide Fragments / metabolism*
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Recombinant Proteins / metabolism
  • Transcription, Genetic
  • Transfection
  • beta Catenin / metabolism

Substances

  • Adenomatous Polyposis Coli Protein
  • Peptide Fragments
  • Recombinant Fusion Proteins
  • Recombinant Proteins
  • beta Catenin
  • Green Fluorescent Proteins
  • Luciferases
  • Caspase 3
  • Caspases