Protein phosphorylation is an essential part of the activating and regulatory processes in the functioning and responses for a variety of cells. Attention has been paid to protein phosphorylation in neutrophils because of the importance of this leukocyte in defense against infection and in a number of allergic and non-allergic tissue-damaging inflammatory reactions. The ultimate purpose of the proposed investigation is to identify, isolate and characterize those proteins which are phosphorylated when neutrophils are stimulated by chemotactic factors, cytokines and crosslinking of Fc receptors and the respective protein kinases for which they are responsible. Attempts will be made to identify the function of phosphorylated proteins, the role that phosphorylation plays in these respective functions and what role the proteins and their phosphorylation play in neutrophil stimulus-response coupling. For these purposes, the following studies are being pursued:

(1) To define the varieties of neutrophil protein kinases (tyrosine protein kinases, mitogen-activated protein kinase (MAP kinase), MAP kinase-activated protein kinase 2, calcium/calmodulin-dependent protein kinase, histone H4 protein kinase, protein kinase C and others); the regulation and the mechanism of activation of these kinases and their respective substrates in various subcellular fractions of neutrophils.

(2) To define the phosphoproteins, the phosphorylation levels of which are regulated by chemotactic factors (fMet-Leu-Phe), cytokines, crosslinking of Fc receptors, calcium ionophores and phorbol esters in intact neutrophils. Attempts will be made to identify and characterize the molecular components (protein kinases and their substrates) of the physiologically important phosphorylation system in neutrophils.

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