Mh. Pillinger et al., MITOGEN-ACTIVATED PROTEIN-KINASE IN NEUTROPHILS AND ENUCLEATE NEUTROPHIL CYTOPLASTS - EVIDENCE FOR REGULATION OF CELL-CELL ADHESION, The Journal of biological chemistry, 271(20), 1996, pp. 12049-12056
We employed neutrophils and enucleate neutrophil cytoplasts to study t
he activation of the mitogen-activated protein kinases (MAPKs) p44(erk
1) and p42(erk2) in neutrophils by inflammatory agonists that engage G
protein-linked receptors. Formyl-methionyl-leucyl-phenylalanine (FMLP
) rapidly and transiently activated MAPK in neutrophils and cytoplasts
, consistent with a role in signaling for neutrophil functions. FMLP s
timulated p21(ras) activation in neutrophils and Raf-1 translocation f
rom cytosol to plasma membrane in cytoplasts, with kinetics consistent
with events upstream of MAPK activation. Insulin, a protein tyrosine
kinase receptor (PTKR) agonist, stimulated neutrophil MAPK activation,
demonstrating an intact system of PTKR signaling in these post-mitoti
c cells. FMLP- and insulin-stimulated MAPK activation in cytoplasts we
re inhibited by Bt(2)cAMP, consistent with signaling through Raf-1 and
suggesting a mechanism for cAMP inhibition of neutrophil function. Ho
wever, Bt(2)cAMP had no effect on FMLP-stimulated MAPK activation in n
eutrophils. The extent of MAPK activation by various chemoattractants
correlated with their capacity to stimulate neutrophil and cytoplast h
omotypic aggregation. Consistent with its effects on MAPK, Bt(2)cAMP i
nhibited FMLP-stimulated aggregation in cytoplasts but not neutrophils
. Insulin had no independent effect but primed neutrophils for aggrega
tion in response to FMLP. Our studies support a p21(ras)-, Raf-1-depen
dent pathway for MAPK activation in neutrophils and suggest that neutr
ophil adhesion may be regulated, in part, by MAPK.