FIGURE 3.
Tyrosine phosphorylation of HS1 is induced by fMLP and is mediated by adhesion and Src family kinases. A and C, immunoblot of HS1 immunoprecipitation from PLB-985 cells treated with fMLP (1 μm) and blotted for total phospho-tyrosine (A), or immunoblot of phospho-HS1(Y397) from cells treated with fMLP (1 μm) (C). Note maximal tyrosine phosphorylation of HS1 after 3 min with fMLP. Adhesion to fibrinogen (10 μg/ml) was necessary for significant HS1 phosphorylation. Treatment of cells plated on fibrinogen with PP2 (10 μm) impaired tyrosine phosphorylation in response to fMLP. B and D, quantification of HS1 tyrosine phosphorylation (B), or phospho-HS1 (Y397) (D). The ratio of phospho-HS1 to total HS1 was quantified and graphed relative to unstimulated cells in suspension. Graph represents mean ratio ± S.E. from at least three independent experiments. *, p < 0.05 by one-way ANOVA with Tukey post-test compared with unstimulated cells. Immunoblots are representative of three independent experiments.