Induction of tyrosine phosphorylation and association of beta-catenin with EGF receptor upon tryptic digestion of quiescent cells at confluence

Oncogene. 1997 Jul 3;15(1):71-8. doi: 10.1038/sj.onc.1201160.


Normal human breast epithelial (HBE) cells which reached confluence ceased growth and tightly adhered to each other, forming a monolayer. In quiescent cells thus arrested by density, E-cadherin colocalized and coimmunoprecipitated with alpha- and beta-catenins in the boundary region between adjacent cells. By contrast, immunocytostaining and Western blot analyses revealed that E-cadherin colocalized and coprecipitated with beta-catenin but not with alpha-catenin in exponentially growing cells at low density. As a comparable amount of alpha-catenin was detected in the total cell lysate of cells at different densities, it is suggested that alpha-catenin is present but dissociates from the E-cadherin-beta-catenin complex in growing cells. beta-Catenin was tyrosine phosphorylated in growing cells at low density but not in quiescent cells at confluence. Tyrosine phosphorylation of beta-catenin was concomitantly induced with association of beta-catenin with EGF receptor (EGFR) when quiescent cells at confluence were dissociated into single cells by tryptic digestion, being accompanied by dissociation of alpha-catenin from E-cadherin. Both tyrosine phosphorylation and association of beta-catenin with EGFR were inhibited by tyrphostin, a specific inhibitor of the EGFR tyrosine kinase, whereas dissociation of alpha-catenin from E-cadherin was not. The results suggest that tyrosine phosphorylation of beta-catenin is achieved by EGFR upon tryptic digestion of cells and concurrent with but independent of dissociation of alpha-catenin from E-cadherin. beta-Catenin thus phosphorylated at tyrosine is suggested to play the role in preventing alpha-catenin once dissociated from reassociating with E-cadherin until cells reach confluence.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Breast
  • Cadherins / metabolism
  • Cell Count
  • Cell Division
  • Cells, Cultured
  • Cytoskeletal Proteins / metabolism*
  • Enzyme Induction
  • Epithelium
  • ErbB Receptors / metabolism*
  • Humans
  • Phosphorylation
  • Phosphotyrosine / analysis
  • Trans-Activators*
  • Tyrosine / metabolism*
  • beta Catenin


  • CTNNB1 protein, human
  • Cadherins
  • Cytoskeletal Proteins
  • Trans-Activators
  • beta Catenin
  • Phosphotyrosine
  • Tyrosine
  • ErbB Receptors