DISTURBED INTERACTION OF P21-RAC WITH MUTATED P67-PHOX CAUSES CHRONICGRANULOMATOUS-DISEASE

Chronic granulomatous disease (CGD) is characterized by the failure of phagocytic leukocytes to generate superoxide, needed for the intracel lular killing of microorganisms. This is caused by mutations in any on e of the four subunits of the nicotinamide adenine dinucleotide phosph ate (NADPH) oxidase. In a rare. autosomal recessive form of CGD, a 67- kD cytosolic component of this enzyme (p67-phox) is missing. We here r eport on a patient with a mutation in the p67-phox gene that leads to expression of a nonfunctional p67-phox protein. The purified granulocy tes of this patient failed to produce superoxide and contained about h alf of the normal amount of p67-phox. Analysis of the cDNA and genomic DNA of this this patient showed that the patient is a compound hetero zygote for a triplet nucleotide deletion in the p67-phox gene, predict ing an in-frame deletion of lysine 58 in the p67-phox protein and a la rger deletion of 11-13 kb in the other allele, Interestingly, the (58) Lys deletion in p67-phox disrupts the interaction with p21-rac1, a ras -related protein involved in the activation of the NADPH oxidase. In c ontrast to normal neutrophils, in which p47-phox and p67-phox transloc ate to the plasma membrane upon cell activation, the cells of the pati ent did not show this translocation, indicating that an interaction be tween p67-phox and p21-rac1 is essential for translocation of these cy tosolic proteins and activation of the NADPH oxidase. Moreover, this C GD patient represents the first case of a disease caused by a disturbe d binding of a ras-related protein to its target protein.