Overexpression of wild-type SHIP downregulates FcγR-induced Rac activation. (A) Raw 264.7 cells were retrovirally infected using vector alone, wild-type SHIP, or catalytic-deficient D675A SHIP. GTP-bound Rac was measured in these transfectants after FcγR clustering. The bottom panel represents the band intensity of the Rac GTP. Values obtained from 3 independent experiments are represented as mean and SEM. (B) The stable transfectants were analyzed for SHIP expression by immunoprecipitating SHIP with rabbit polyclonal SHIP antibody and immunoblotting with SHIP antibody. The last lane is a control immunoprecipitate (IP) with normal rabbit serum. Data were analyzed by the Student t test (*P ≤ .05).