Protein-tyrosine phosphorylations induced by concanavalin A and N-formyl-methionyl-leucyl-phenylalanine in human neutrophils

Abstract

The ability of the lectin concanavalin A (ConA) and N‐formyl‐methionyl‐leucyl‐phenylalanine (fMLF) to induce protein‐tyrosine phosphorylation in human neutrophils was examined by immunoblot analysis. ConA caused an increase in tyrosine phosphorylation of protein bands with apparent molecular masses of 120, 80, 76, 66 and 40 kDa; on the other hand, fMLF caused an increase in those of only 80‐kDa and 40‐kDa proteins. These protein‐tyrosine phosphorylations were time‐ and dose‐dependent. The tyrosine phosphorylation of 40‐kDa protein induced by fMLF was suppressed but that by ConA was not suppressed by pertussis toxin pretreatment. At the same time, pertussis toxin pretreatment also inhibited lysozyme release and aggregation of neutrophils induced by fMLF but did not inhibit those responses induced by ConA. These results suggest that the tyrosine phosphorylation of 40‐kDa protein may be involved in a part of neutrophil activation and be regulated via pleiotropic signal transduction pathways. In addition, immunoblot analysis employing antibodies against microtubule‐associated protein 2 (MAP2) kinase suggested that this tyrosine‐phosphorylated 40‐kDa protein might be the MAP2 kinase.