Figure 5

The effect of PIP knockdown on ERK-Akt and integrin-β1signaling. (A) Western blot analysis to measure the levels of phosphorylated (Ph)-ERK, total (T)-ERK, ph-Akt, and T-Akt following PIP-knockdown with siRNA duplex1 (PIP-D1) and duplex2 (PIP-D2) in MDA-MB-453 cell line. Fold changes of Phospho/Total ratios (Ph/T-RR) were assessed relative to non-targeting siRNA control (CTL). (B) Western blot analysis to measure the level of ph-CREB1, T-CREB1, and ILK1 following PIP-knockdown as described in (A). Ph-ATF1 is the phosphorylated form of CREB-related protein that is known to be detected by this antibody. (C) Integrin-β1 immunoprecipitation (IP). IP assays were carried out with Integrin-β1 following PIP-knockdown with PIP-D1 and PIP-D2 in MDA-MB-453 cell line. Non-targeting siRNA was used as control (CTL). Western blot analysis was carried out on IP samples to measure the integrin-β1 binding to ILK1 and ErbB2. Immunoblotting with integrin-β1 antibody was used as a loading control. Fold changes (RR) of ILK1 and ErbB2 following PIP-knockdown were measured relative to that of control-siRNA. (D) Integrin-β1 immunoprecipitation following PIP-knockdown and the addition of fibronectin fragments (Fn-fs). PIP-knockdown with PIP-D1 was carried out as described in (C). Twenty-four hours after PIP-knockdown, cells were treated with α-chymotryptic fibronectin fragment 120K at 100 µg/ml concentration. Control cells were treated with vehicle only. Fold changes (RR) of ILK1 and ErbB2 following PIP-knockdown + Fn-fs were measured relative to the control. (E) The effect of fibronectin fragments on cell invasion following PIP-knockdown. Cell invasion assays were carried out after PIP-knockdown with PIP-D1 in MDA-MB-453 cell line. Transfection with non-targeting siRNA control (CTL) was used as a control. Treatment with fibronectin fragments was carried out as described in (D). Error Bars: ± 2SEM. Δ; is the difference between CTL and PIP-D1+Fn-fs groups. ERK, extracellular signal-regulated kinase; ILK1, integrin-linked kinase 1; RR, relative risk; SEM, standard error of the mean.