Syk activates the RhoA pathway in C3bi-CR3 signaling. Macrophage-like differentiated Day3-HL60, DN-Syk/HL (clone 8), Syk-siRNA/HL (clone 6), control siRNA/HL (clone 4), or Flag-rescue–Syk/Syk-siRNA/HL cells were incubated with serum-opsonized zymosan for indicated times and immunoblotting analysis was performed. (A) The cell lysates were incubated with GST-rhotekin RBD immobilized on glutathione-Sepharose. GTP-bound RhoA was detected by immunoblotting analysis with anti-RhoA polyAb. The same amounts of cell lysates were also immunoblotted with anti-RhoA polyAb. (B) The cell lysates were immunoprecipitated with anti-Vav polyAb and immunoblotted with antiphosphotyrosine monoAb. The reprobing analysis was also done with anti-Vav polyAb. These blots are representative of 3 independent experiments.