ACTIVATION OF P38 IN STIMULATED HUMAN NEUTROPHILS - PHOSPHORYLATION OF THE OXIDASE COMPONENT P47(PHOX) BY P38 AND ERK BUT NOT BY JNK

Incubation of human neutrophils with FMLP, a chemotactic peptide, or P MA, a stimulator of protein kinase C, resulted in the activation of p3 8, a proline-directed kinase. Previous studies had shown that extracel lular signal-regulated kinase (ERK), another proline-directed kinase, was activated with similar kinetics in neutrophils stimulated with FML P and PMA (1, 2). Because one possible target for these proline-direct ed kinases is p47(phox), a component of the respiratory burst oxidase, we examined the phosphorylation of this protein by p38 and ERK, as we ll as JNK, another proline-directed kinase present in neutrophils. We found that both p38 and ERK phosphorylated p47(phox) at the same site and at similar rates, but that p47(phox) was not a substrate for JNK. These data show that p38, like ERK, can be activated in neutrophils ex posed to an appropriate stimulus, and that some but not all proline-di rected kinases are able to participate in the phosphorylation of a pro tein essential for normal neutrophil function. (C) 1996 Academic Press , Inc.