Altered Cell Adhesion Activity by Pervanadate Due to the Dissociation of α-Catenin from the E-Cadherin·Catenin Complex*

Abstract

Leukemia cells (K562) that grow as non-adhesive single cells and have no endogenous cadherin were transfected with an E-cadherin expression vector, and cell clones stably expressing E-cadherin on their surface were established. The expression of E-cadherin induced the up-regulation of catenins, and E-cadherin became associated with catenins. The transfected cells grew as floating aggregates. Cell aggregation was Ca²⁺-dependent and was inhibited by E-cadherin antibodies. The aggregates dissociated into single cells on the addition of pervanadate. Pervanadate caused a dramatic augmentation of the phosphorylation of E-cadherin, β-catenin, and γ-catenin (plakoglobin), but α-catenin was not detectably phosphorylated. After pervanadate treatment, β-catenin and γ-catenin migrated more slowly on gel electrophoresis, suggesting changes in their conformations due to eventual changes in their phosphorylation levels. In the treated cells, a significant amount of α-catenin was dissociated from the E-cadherin·catenin complex. Aggregates of cells expressing an E-cadherin chimeric molecule covalently linked with α-catenin were not dissociated on pervanadate treatment, supporting the idea that the dissociation of α-catenin from the complex underlies the observed E-cadherin dysfunction.