A possible role for protein phosphorylation in the activation of the respiratory burst in human neutrophils. Evidence from studies with cells from patients with chronic granulomatous disease.

Abstract

Two-dimensional gel electrophoresis was used to study protein phosphorylation in granules, membranes, and soluble fractions from human neutrophils that had been loaded with 32Pi. In resting cells, label was incorporated primarily into proteins of the membranes and the soluble supernatant; little appeared in the granules. Activation of 32P-loaded neutrophils resulted in an increase in the 32P content of a small number of membrane and soluble proteins without a change in the labeling of the granule fraction. The identity of the proteins affected by activation depended on the activating agent used; all of the activating agents, however, caused an increase in the labeling of a group of approximately 48-kDa proteins that appeared to be distributed between the membranes and the soluble supernatant. To investigate the role of phosphorylation in the activation of the respiratory burst oxidase, the incorporation of 32P into phosphoproteins was studied in neutrophils from patients with chronic granulomatous disease. When these cells were exposed to phorbol myristate acetate, one of the agents used for the activation of normal neutrophils, the 48-kDa proteins in the membranes and supernatants failed to take up additional 32P. Phosphorylation patterns in normal neutrophils activated under nitrogen were similar to the patterns seen with cells activated in air, suggesting that the differences in phosphorylation between normal and chronic granulomatous disease neutrophils did not represent secondary effects of the oxidants produced by the normal cells, but reflected primary biochemical differences between the normal and the defective phagocytes. We postulate from these results that the uptake of phosphate by the 48-kDa protein group may be involved in the activation of the respiratory burst oxidase.