Fig. 4. Endogenous BMX regulates FAK through phosphorylation of the Tyr^576/577 site.

(A and B) BMX-targeted or control siRNA–transfected LNCaP cells (A) or VCS2 cells (B) were serum-starved for 72 hours and then serum-stimulated for the indicated times, and whole-cell lysates were immunoblotted as indicated. Band intensity ratios in this experiment for the phosphorylated versus total FAK are shown in lower panels. At 20 to 30 min of serum stimulation in three independent experiments, the mean pFAK band intensity ratio in LNCaP cells transfected with control versus BMX siRNA was 2.03 ± 0.27 SEM (P < 0.05). From three independent VCS2 cell experiments at 10 to 20 min, this ratio was 2.77 ± 0.59 SEM (P < 0.05) for the control versus BMX siRNA–transfected cells. (C) BMX-targeted or control siRNA–transfected VCS2 cells were serum-starved for 72 hours, and then trypsinized and kept in suspension for 1 hour followed by plating onto FN-coated dishes for the indicated times. From three independent experiments at 30 to 45 min after plating, the mean of pFAK band intensity ratios for the control versus BMX siRNA–transfected cells was 1.51 ± 0.11 SEM (P < 0.05). (D) Bmx⁺ or Bmx⁻ male MEFs were suspended for 1 hour (Ctrl) and then plated onto FN-coated dishes for 30 min (FN). A blot representative of three independent experiments is shown.