We also show that Arf 6 couples CD 16 to the lipid modifying enzymes phosphatidylinositol4phosphate 5 kinase type 1 alpha ( PI5KIalpha ) and phospholipase D ( PLD ) that are involved in the control of granule secretion ; Arf 6 , but not Rho family small G proteins RhoA and Rac 1 , is required for receptor induced PI5KIalpha membrane targeting as well as for PI5KIalpha and PLD activation . ^^^