Figure 9.

Tyrosine phosphorylation and protein composition of E-cadherin complexes in control versus src-transformed keratinocytes. Keratinocytes under low calcium conditions were infected with either a green fluorescent protein control adenovirus (Ad-GFP) or a virus expressing constitutively active c-src (Ad-src). 24 h after infection cells were incubated in either low (L) or high (H) calcium medium for additional 9 h, in parallel with control uninfected cells (Uninf.). Keratinocytes were lysed in 0.5% NP-40 lysis buffer, and immunoprecipitated with mAbs against E-cadherin. Samples were analyzed by SDS-PAGE and anti-phosphotyrosine immunoblotting (p-Tyr, left). The same blot was subsequently reprobed with antibodies against α-catenin (α-cat.), β-catenin, and γ-catenin (β/γ-cat.), E-cadherin (EC), and Src as indicated (right panels). The asterisk on the anti-phosphotyrosine immunoblot indicates one of the additional tyrosine phosphorylated proteins that are present in the E-cadherin immunoprecipitates from Src-expressing cells, and which become more evident after prolonged exposures.