Fig. 6. ß1 integrin mediates the effects of ECM on E-cadherin targeting to the lateral membrane. Caco-2 cells were plated at 125,000 cells/cm² on plastic, native LN5-rich ECM, type IV collagen or LN2 in the presence or absence of either anti-ß1- or anti-6-integrin blocking antibodies. Cells were then processed for immunofluorescence with anti-E-cadherin and FITC (green) or TRITC-conjugated phalloidin (red) and analysed by confocal microscopy. Colocalization (yellow merge signal) of E-cadherin and actin at the apical-lateral side of cells was estimated by computer analysis of confocal stack series. (A) shows that ECM components increase the colocalization of E-cadherin and actin as compared to plastic without ECM, as expressed in arbitrary units. (B) 3D reconstruction of cells grown on type IV collagen in the absence (a) or in the presence (b) of anti-ß1-integrin blocking antibody (bar, 10µm). The result is representative of three independent experiments. (C) Effect of anti-ß1-integrin blocking antibody on the colocalization of E-cadherin and actin in cells grown on LN2. (D) Effect of anti-6-integrin blocking antibody on the colocalization of E-cadherin and actin in cells grown on native LN5-rich ECM. Note that anti-ß1 antibody treatment results in delocalization of the E-cadherin-actin in cells grown on native ECM, type IV collagen and LN2. Data, expressed as the percentage of control in absence of blocking antibody, are means ±s.e.m. of three independent cultures performed in triplicate. ^*, ^**, and ^*** differ from the control at P<0.05, P<0.01 and P<0.001, respectively.