Foreign particles in serum activate human neutrophils by binding to specific receptors on the cell surface. Ligand binding causes a signal to be transduced through the membrane which activates many intracellular processes. Some of the processes in the mechanism for particle destruction include protein phosphorylation, phagocytosis of the particle, and the production and secretion of toxic oxygen species (i.e. superoxide anion and hydrogen peroxide) and intracellular granule contents. In pathological cases of altered neutrophil function, such as in chronic granulomatous disease or specific granule deficiency, severe infections and potentially lethal situations may quickly arise from the neutrophil's inability to accomplish all phases of the destructive process. The long term goal of this project is to detail the mechanism for activating immune functions through protein phosphorylation. Protein kinase C (PKC), which is calcium and phospholipid-dependent, has been implicated as a regulator of several neutrophil immune functions. Specifically, this project will lead to: (1) a detailed model for protein kinase C (PKC) translocation and its binding to membranes; (2) the characterization of substrates for PKC which, when phosphorylated, may potentiate the stimulatory signal; (3) further characterization of an endogenous protein kinase C inhibitor (PKC-I) with special regard for its role as a modulator of PKC. In general, knowledge of these mechanisms, obtained through unique complimentary biochemical and morphological approaches, will further our understanding of neutrophil immune functions through protein phosphorylation.
