TRANSLOCATION OF P21(RAC2) FROM CYTOSOL TO PLASMA-MEMBRANE IS NEITHER NECESSARY NOR SUFFICIENT FOR NEUTROPHIL NADPH OXIDASE ACTIVITY

Activation of the membrane-associated NADPH oxidase of neutrophils requires several cytosolic factors including p47(phox), p67(phox) and p21(rac2), We compared NADPH oxidase activity with the membrane translocation of p47(phox), p67(phox), and p21(rac2), In a cell-free system, GTP gamma S stimulated translocation of p47(phox) and p67(phox) to the plasma membrane only in the presence of arachidonate, and this translocation correlated with NADPH oxidase activity of the reisolated plasma membranes (R = 0.94 and 0.97, respectively), In contrast, GTP gamma S-stimulated p21(rac2) translocation with or without arachidonate, and the extent of translocation did not correlate with oxidase activity (R = 0.17), Neutrophil cytoplasts were used to relate membrane translocation of p47(phox), p67(phox) and p21(rac2) to membrane oxidase activity in response to the inflammatory agonists, Whereas N-formyl-methionyl-leucyl-phenylalanine stimulated equimolar, transient membrane translocation of p47(phox) and p67(phox) which kinetically paralleled NADPH oxidase activity, relatively little p21(rac2) translocated (moles of p47(phox)/p21(rac2) = 16.6), Moreover, although phorbol 12-myristate 13-acetate stimulated both the stable translocation of p47(phox) and p67(phox) and sustained NADPH oxidase activity, it did not stimulate p21(rac2) translocation, From these data we conclude that membrane translocation of p21(rac2) does not regulate NADPH oxidase activity stoichiometrically.