MECHANISMS OF NADPH OXIDASE ACTIVATION IN HUMAN NEUTROPHILS - P67(PHOX) IS REQUIRED FOR THE TRANSLOCATION OF RAC-1 BUT NOT OF RAC-2 FROM CYTOSOL TO THE MEMBRANES

NADPH oxidase is the enzyme complex responsible for the production of oxygen radicals in phagocytes. On neutrophil stimulation, the cytosoli c components of NADPH oxidase, p67(phox) and p47(phox), as well as the Ras-related G-protein rac 2, are translocated from the cytosol to cel l membranes where they associate with a flavocytochrome b to form a fu nctional complex. Besides rac 2, rac 1 G-protein is also involved in t he activation of the NADPH oxidase, but, to date, it has not been docu mented whether it is also translocated in activated neutrophils. In th is paper we show that: (a) in neutrophils stimulated with formylmethio nyl-leucylphenylalanine, concanavalin A or phorbol 12-myristate 13-ace tate, both rac 1 and rac 2 are translocated from cytosol to the membra nes; (b) in neutrophils from patient with a form of chronic granulomat ous disease in which p67(phox) is absent, rac 2 and p47(phox) were tra nslocated as in normal neutrophils on stimulation with the above agoni sts, but rac 1 failed to be translocated from the cytosol to the membr anes. This is the first demonstration that, in activated neutrophils, rac 1 is translocated from the cytosol to the membranes and this trans location requires p67(phox). These results, coupled with those showing that rac 2 is not translocated in activated neutrophils lacking p47(p hox) [El Benna, Ruedi and Babior (1994) J. Biol. Chem. 269, 6729-6734] , may suggest that the assembly of the cytosolic components of NADPH o xidase on the plasma membrane takes place through selective coupling o f activated rac 1 and rac;2 with p67(phox) and p47(phox) respectively.