SRC tyrosine kinase activity is required for P-selectin–triggered CD18 redistribution to Triton X-100–insoluble cytoskeletal fraction and colocalization of Mac-1 clusters with F-actin patches at the site of cell-cell contact.

PMNLs were preincubated for 1 minute at 37°C with DMSO or 25 μM PP1 before the addition of 10 μg/mL P-selectin–IgG chimera. (A) Coincubation in standard conditions was stopped at different times. Samples were processed, and the presence of CD18 in Triton X-100–insoluble cytoskeletal fraction was analyzed as in Figure 4. (B) PMNLs, pretreated with DMSO (i-iii) or with 25 μM PP1 (iv-vi), were stimulated by 10 μg/mL P-selectin–IgG chimera for 2 minutes. After stimulation, CD11b and F-actin were stained and processed for confocal laser scanning microscopy as in Figure 4. Panels i, ii, and iii show an aggregate of 2 cells. Panels i and iv show F-actin staining, ii and v show CD11b staining. In the overlay (iii, vi), yellow represents colocalization of the 2 stainings. The figure is representative of results obtained in 5 different experiments.