Abstract
In order to elucidate the role of mitogen-activated protein kinase kinase (MEK-1/2) in 5-lipoxygenase (5-LO) activation we studied the N-formyl-methionyl-leucyl-phenylalanine (fMLP)-induced 5-LO translocation in human blood neutrophils (PMNs). In non-primed, Ca(2+)-repleted PMNs, fMLP consistently stimulated MEK-1/2 phosphorylation, but induced 5-LO translocation and product formation (430+/-128 pmol; SEM, n=13) only in 13 of 18 PMN preparations from different healthy donors. In fMLP-responsive cells, the MEK-1/2 inhibitor PD098059 (50 microM) attenuated MEK phosphorylation and abolished 5-LO activation at the translocation step. The fMLP-mediated 5-LO product formation was also sensitive to MEK inhibition by U0126 and to p38 inhibition by SB203580. But in contrast to PD098059, U0126 at 10 microM and SB203580 at 20-50 microM impaired 5-LO activity in the cell-free assay setting, suggesting direct actions of higher concentrations of U0126 and SB203580 on 5-LO apart from MEK and p38 inhibition, respectively. These data show that fMLP initiates 5-LO product formation in non-primed, Ca(2+)-repleted human blood PMNs from healthy donors, and that MEK signaling is pivotal, but not sufficient for 5-LO activation in response to the receptor agonist fMLP.
Publication types
-
Research Support, Non-U.S. Gov't
MeSH terms
-
Arachidonate 5-Lipoxygenase / metabolism*
-
Butadienes / pharmacology
-
Calcimycin / pharmacology
-
Calcium / metabolism
-
Calcium / pharmacology
-
Cell-Free System
-
Enzyme Activation / drug effects
-
Flavonoids / pharmacology
-
Humans
-
Imidazoles / pharmacology
-
MAP Kinase Kinase 1
-
MAP Kinase Kinase 2
-
MAP Kinase Signaling System / drug effects*
-
Mitogen-Activated Protein Kinase Kinases / antagonists & inhibitors*
-
Mitogen-Activated Protein Kinase Kinases / metabolism
-
N-Formylmethionine Leucyl-Phenylalanine / pharmacology*
-
Neutrophils / drug effects*
-
Neutrophils / enzymology
-
Neutrophils / metabolism
-
Nitriles / pharmacology
-
Phosphorylation / drug effects
-
Protein Serine-Threonine Kinases / antagonists & inhibitors*
-
Protein Serine-Threonine Kinases / metabolism
-
Protein Transport / drug effects
-
Protein-Tyrosine Kinases / antagonists & inhibitors*
-
Protein-Tyrosine Kinases / metabolism
-
Pyridines / pharmacology
Substances
-
Butadienes
-
Flavonoids
-
Imidazoles
-
Nitriles
-
Pyridines
-
U 0126
-
Calcimycin
-
N-Formylmethionine Leucyl-Phenylalanine
-
Arachidonate 5-Lipoxygenase
-
MAP2K2 protein, human
-
Protein-Tyrosine Kinases
-
Protein Serine-Threonine Kinases
-
MAP Kinase Kinase 1
-
MAP Kinase Kinase 2
-
MAP2K1 protein, human
-
Mitogen-Activated Protein Kinase Kinases
-
SB 203580
-
2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one
-
Calcium