Circulating human neutrophils exhibited low rates of protein biosynthesis, as determined by their ability to incorporate [35S]methionine into TCA-precipitable material. Exposure of cells to the chemotactic peptide (N-formyl-L-methionyl-L-leucyl-L-phenylalanine) increased their rate of protein synthesis, and the maximal stimulation of biosynthesis by this inflammatory agent was observed at 0.1 μM: this concentration of chemotactic peptide “primed” neutrophil activity and only activated the oxidase of these cells by 8% of maximum. The newly-synthesized proteins were analyzed by two-dimensional polyacrylamide gel electrophoresis and compared with those synthesized in control cells. Two classes of proteins were observed in “primed” cells. The first of these comprised proteins whose rate of biosynthesis changed very little upon “priming” whereas the second class comprised proteins whose rate of synthesis increased greatly after exposure to chemotactic peptide. The fMet-Leu-Phe stimulated protein synthesis was inhibited by actinomycin D and cycloheximide showing that this phenomenon required both transcription and translation. We propose that these fMet-Leu-Phe regulated proteins play an important role in the function of neutrophils during an inflammatory response.

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