Chemotactic factor induced tyrosine phosphorylation of membrane associated proteins in rabbit peritoneal neutrophils.

Protein tyrosine phosphorylation in rabbit peritoneal neutrophils was examined by immunoblotting with antibodies specific for phosphotyrosine. Two tyrosine phosphorylated proteins were found with apparent molecular weights of 62,000 (p62) and 125,000. Both were enriched in the membrane fraction. Stimulation of the neutrophils with chemotactic factor fMet-Leu-Phe (10(-8)M, 20 sec) but not phorbol 12-myristate-13-acetate (0.1 microgram/ml, 10 min) caused rapid increase in tyrosine phosphorylation. The effect of fMet-Leu-Phe was inhibited by the pretreatment of neutrophils with pertussis toxin. The p62 protein was also recognized by antibody raised against a synthetic fragment commonly found in the tyrosine kinases of the src gene family. The results indicate that stimulation of the tyrosine phosphorylation of membrane associated proteins is one of the early events occurring in activated neutrophil and this stimulation of tyrosine phosphorylation may be regulated by a GTP-binding protein.