Loss of density-dependent growth inhibition and dissociation of alpha-catenin from E-cadherin

J Cell Physiol. 1997 Oct;173(1):54-63. doi: 10.1002/(SICI)1097-4652(199710)173:1<54::AID-JCP7>3.0.CO;2-I.

Abstract

Normal human breast epithelial (HBE) cells at early (9th) passage ceased growth and formed a monolayer when they reached confluence. Immunostaining and Western blotting revealed that alpha- and beta-catenins colocalized and coprecipitated with E-cadherin, suggesting a complex formation of E-cadherin with alpha- and beta-catenins in early passage cells. In contrast, HBE cells at late (12-13th) passage did not cease growth after confluence but stratified. The late passage cells exhibited enhanced colony forming ability in soft agar compared with early passage cells, however, they had a definite proliferating lifespan and were primarily diploid. In late passage cells grown as multilayers, alpha-catenin was expressed but did not colocalize or coprecipitate with E-cadherin, suggesting its dissociation from E-cadherin. Coimmunoprecipitation of alpha-actinin with alpha-catenin suggested an indirect link between the E-cadherin-beta-catenin complex and alpha-actinin via alpha-catenin in early, but not in late passage cells. Beta-Catenin in late passage cells was tyrosine phosphorylated and was not dephosphorylated following the addition of inhibitors of tyrosine kinases. Inhibition of dephosphorylation of beta-catenin in early passage cells by vanadate, an inhibitor of protein tyrosine phosphatases, caused overgrowth of cells beyond the saturation density and loss of alpha-catenin from the E-cadherin-beta-catenin complex. The results suggest that E-cadherin requires its association with alpha-actinin-associated alpha-catenin to maintain epithelial monolayers and accomplish the density-dependent inhibition of growth. In addition, association between E-cadherin and alpha-catenin is suggested to be prevented by the presence of tyrosine phosphorylated beta-catenin which associates with E-cadherin.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actinin / metabolism
  • Antibodies, Monoclonal
  • Breast
  • Cadherins / immunology
  • Cadherins / metabolism*
  • Cell Division* / drug effects
  • Cell Line
  • Cytoskeletal Proteins / immunology
  • Cytoskeletal Proteins / metabolism*
  • Electrophoresis, Polyacrylamide Gel
  • Humans
  • Immunohistochemistry
  • Phosphorylation
  • Precipitin Tests
  • Protein-Tyrosine Kinases / antagonists & inhibitors
  • Trans-Activators*
  • Vanadates / pharmacology
  • alpha Catenin
  • beta Catenin

Substances

  • Antibodies, Monoclonal
  • CTNNA1 protein, human
  • CTNNB1 protein, human
  • Cadherins
  • Cytoskeletal Proteins
  • Trans-Activators
  • alpha Catenin
  • beta Catenin
  • Actinin
  • Vanadates
  • Protein-Tyrosine Kinases