Effect of RGDS peptide on the SLF-induced enhancement of pp125^FAK tyrosine phosphorylation. (A) TF-1 cells were plated on the fibronectin-coated wells and incubated for 15 minutes at 37°C. Wells were washed twice with RPMI-BSA medium. Medium without (lane 1) or with SLF (10 ng/mL) (lanes 2 to 6) containing RGES peptide (0.5 mg/mL) (lane 3), RGDS peptide (0.5 ng/mL) (lane 4), RGDS plus anti-α4 MoAb (lane 5), or anti-α4 MoAb (10 μg/mL) (lane 6) was added to the wells. After a 10-minute incubation, cells were lysed and subjected to immunoprecipitation with anti-pp125^FAK MoAb. The immunoprecipitates were then blotted with anti-p-Tyr MoAb (upper panel). The Western blot membrane that was probed with the anti-p-Tyr MoAb in the upper panel was stripped and probed with anti-pp125^FAK polyclonal antibody (lower panel). This is a representative result from three separate experiments. (B) Relative tyrosine phosphorylation of FAK was determined by densitometry and was normalized by relative FAK amount in these immunoprecipitates. The values represent the mean ± standard deviation (SD) of three separate experiments. *P < .005 versus control, **P < .05 versus SLF.