A 68-KDA KINASE AND NADPH OXIDASE COMPONENT P67(PHOX) ARE TARGETS FOR CDC42HS AND RAC1 IN NEUTROPHILS

Cdc42Hs and Rad are members of the Ras superfamily of small molecular weight (p21) GTP binding proteins. Cdc42Hs induces filopodia formation in Swiss 3T3 fibroblasts while Rad induces membrane ruffling. Rad also activates superoxide production by the components (cytochrome b, p40(phox), p67(phox), and p47(phox)) Of the neutrophil oxidase. To isolate target proteins involved in these signaling pathways, we have probed proteins from neutrophil cytosol immobilized on nitrocellulose with Cdc42Hs labeled with [gamma-P-32]GTP. Cdc42Hs probe detected binding protein(s) of 66-68 kDa in neutrophil cytosol. Rad probe also detected the 66-68-kDa proteins, suggesting the possibility that p67(phox) may be a binding protein for both of these p21 proteins. Indeed, Cdc42Hs and Rad were found to bind specifically to purified recombinant p67(phox) but not the other oxidase components. A 68-kDa Cdc42Hs binding protein was purified from neutrophil cytosol and found to be related to the recently described p65(pak) kinase from brain. These results suggest that the p68 kinase and p67(phox) are targets for Cdc42Hs and Rad in neutrophils.