Fig. 6.
Effect of SLF on the tyrosine phosphorylation of paxillin. (A) TF-1 cells in suspension (lanes 1 and 2) or plated on fibronectin-coated wells (lanes 3 and 4) were incubated for 15 minutes at 37°C. Wells were washed twice with RPMI-BSA medium. Medium with SLF (10 ng/mL) (lanes 2 and 4) or without SLF (lanes 1 and 3) were added and the wells were further incubated for 10 minutes. Cells were lysed and subjected to immunoprecipitation with antipaxillin MoAb. The immunoprecipitates were then blotted with anti-p-Tyr MoAb (upper panel). The Western blot transfer membrane that was probed with the anti-p-Tyr MoAb in the upper panel was stripped and probed with antipaxillin MoAb (lower panel). (B) Time course of the SLF-induced enhancement of tyrosine phosphorylation of paxillin. 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 with SLF (10 ng/mL) was added to the wells. The wells were incubated for various time periods. Time of incubation is shown in minutes. Cells were lysed and subjected to immunoprecipitation with antipaxillin MoAb. The immunoprecipitates were then blotted with anti-p-Tyr MoAb (upper panel). The Western blot transfer membrane that was probed with the anti-p-Tyr MoAb in the upper panel was stripped and probed with antipaxillin MoAb (middle panel). The lower graph shows the ratio of tyrosine-phosphorylated paxillin to paxillin protein expression represented by densitometric scanning of transblot bands. Data represent the percentage of control (non-SLF-treated cells) (lower panel). (C) Dose dependence of SLF-induced enhancement of tyrosine phosphorylation of paxillin. 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. The medium with increasing concentrations of SLF was added to the wells. Cells were lysed and subjected to immunoprecipitation with a MoAb directed against paxillin. The immunoprecipitates were then blotted with MoAb directed against p-Tyr (upper panel). The Western blot transfer membrane that was probed with the anti-p-Tyr MoAb in the upper panel was stripped and probed with antipaxillin MoAb (middle panel). The lower graph shows the ratio of tyrosine-phosphorylated paxillin to paxillin protein expression represented by densitometric scanning of transblot bands. Data represent the percentage of control (SLF nontreated cells) (lower panel). The background band at 50 kD is the immunoglobulin heavy chain from the immunoprecipitation. Similar results were obtained in three independent experiments.