Fig. 5. Tyrosine phosphorylation of cortactin is required for ECM degradation at invadopodia. (A) A375MM cells transfected with cortactin^{Y421,466,482F} display a significantly reduced ability to degrade the ECM compared with control cells transfected with cortactin^WT. By contrast, cells transfected with the pseudophosphorylated cortactin^Y421D increased their capacity to degrade the matrix. Data represent the mean ± s.d. of three independent experiments. Statistical significance was evaluated by Student's t-test: wild type vs Y421D and Y421,466,482F, P<0.002. (B) Representative images of A375MM cells transfected with cortactin^Y421D 48 hours after cortactin depletion. Typically, cortactin^Y421D localizes to invadopodia. Scale bar: 10 µm.