Inhibition of Rap1 activity inhibits FcγR-mediated phagocytosis. A, pcDNA3.1-and Rap1GAP-transfected NR8383 macrophages were stimulated with 30/1 IgG-opsonized SRBCs for 7 min, lysed, and assayed for GTP-bound Rap1 as described in Materials and Methods. Aliquots were removed from lysates before incubation with beads and immunoblotted for Rap1 and Rap1GAP. Densitometric analysis was performed for each Western blot as described in Materials and Methods. Data shown represent values relative to untreated pcDNA3.1-and Rap1GAP-transfected macrophages, and are the means ± SE of three independent experiments. *, p < 0.05 compared with vehicle macrophages by Student’s t test. B, pcDNA3.1- and Rap1GAP-transfected macrophages were assessed for phagocytic ability as described in Materials and Methods. NR8383 macrophages preincubated with liposome constructs containing anti-Rap1, anti-RhoA, anti-C3G, or isotype control Ab as detailed in Materials and Methods were assessed for (C) GTP-bound Rap1 and (D) phagocytic ability. Data shown are the means ± SE of three independent experiments. **, p < 0.01 compared with control by Student’s t test.