Actin-dependent membrane association of a Drosophila epithelial APC protein and its effect on junctional Armadillo

Curr Biol. 2000 Nov 2;10(21):1339-48. doi: 10.1016/s0960-9822(00)00770-3.

Abstract

Background: The adenomatous polyposis coli (APC) protein is an important tumour suppressor in the colon. It promotes the destabilisation of free cytoplasmic beta-catenin (the vertebrate homologue of the Drosophila protein Armadillo), a critical effector of the Wnt signalling pathway. The beta-catenin protein is also a component of adherens junctions, linking these to the actin cytoskeleton. In Drosophila epithelial cells, the ubiquitous form of APC, known as E-APC, is associated with adherens junctions. This association appears to be necessary for E-APC to function in destabilising Armadillo.

Results: Using actin-depolymerising drugs, we established that an intact actin cytoskeleton is required for the association of E-APC with adherens junctions in the Drosophila embryo. From an analysis of profilin mutants, whose actin cytoskeleton is disrupted, we found that E-APC also requires actin filaments to associate with adhesive cell membranes in the ovary. Notably, conditions that delocalised E-APC from membranes, including a mutation in E-APC itself, caused partial detachment of Armadillo from adhesive membranes.

Conclusions: Actin filaments are continuously required for E-APC to be associated with junctional membranes. These filaments may serve as tracks for E-APC to reach the adherens junctions. The failure of E-APC to do so appears to affect the integrity of junctional complexes.

MeSH terms

  • Actin Cytoskeleton / drug effects
  • Actin Cytoskeleton / physiology*
  • Actins / metabolism*
  • Adenomatous Polyposis Coli Protein
  • Adherens Junctions / metabolism*
  • Animals
  • Armadillo Domain Proteins
  • Bridged Bicyclo Compounds, Heterocyclic / pharmacology
  • Cell Membrane / metabolism*
  • Cell Size
  • Colchicine / pharmacology
  • Contractile Proteins*
  • Cytochalasin D / pharmacology
  • Cytoskeletal Proteins / metabolism*
  • Drosophila Proteins*
  • Drosophila melanogaster / embryology
  • Drosophila melanogaster / growth & development
  • Drosophila melanogaster / metabolism
  • Embryo, Nonmammalian / cytology
  • Embryo, Nonmammalian / metabolism
  • Female
  • Fluorescent Dyes / metabolism
  • Insect Proteins / immunology
  • Insect Proteins / metabolism*
  • Microfilament Proteins / genetics
  • Microfilament Proteins / metabolism
  • Microscopy, Confocal
  • Microtubules / drug effects
  • Microtubules / metabolism
  • Ovary / cytology
  • Ovary / metabolism
  • Phalloidine / pharmacology
  • Profilins
  • Thiazoles / pharmacology
  • Thiazolidines
  • Trans-Activators*
  • Transcription Factors

Substances

  • APC protein, Drosophila
  • ARM protein, Drosophila
  • Actins
  • Adenomatous Polyposis Coli Protein
  • Armadillo Domain Proteins
  • Bridged Bicyclo Compounds, Heterocyclic
  • Contractile Proteins
  • Cytoskeletal Proteins
  • Drosophila Proteins
  • Fluorescent Dyes
  • Insect Proteins
  • Microfilament Proteins
  • Profilins
  • Thiazoles
  • Thiazolidines
  • Trans-Activators
  • Transcription Factors
  • chic protein, Drosophila
  • Phalloidine
  • Cytochalasin D
  • Colchicine
  • latrunculin A