Fig. 7

GroPIns promotes Shp1-mediated dephosphorylation of cortactin. A Representative images of A375MM cells plated on fluorescent gelatin-coated coverslips and then untreated (Ctr) or treated with 50 µM GroPIns for 3 h. Cells were fixed and stained for pY421-cortactin and cortactin. pY421-cortactin, cortactin and gelatin are shown in green, magenta and gray, respectively. The degraded ECM is shown as dark areas and refers to the degradative activity resulting from ~ 19 h of incubation of cells on the gelatin. Invadopodia present following 3 h of GroPIns treatment are shown as actin-positive dots corresponding to the dark areas. B Quantification of cortactin phosphorylation (expressed as percentage of control) of cells treated with 50 µM GroPIns for the indicated times. Cortactin phosphorylation was expressed as the fold change in pY421-cortactin/cortactin ratio localized to invadopodia. Data are expressed as the means (± SE) of three independent experiments. C Quantification of cortactin phosphorylation of non-targeting siRNAs and Shp-1 siRNAs-treated A375MM cells (left panel) and of empty vector and Shp1 C455S transfected cells (right panel) left untreated (Ctr) or treated with 50 µM GroPIns for 3 h. Data are expressed as the means (± SE) of two independent experiments performed in duplicate. ***P < 0.001; **P < 0.02; *P < 0.05; ns P > 0.05 (Student’s t-test) calculated for each treatment versus untreated samples. Scale bars, 10 μm