Distinct ligand-dependent roles for p38 MAPK in priming and activation of the neutrophil NADPH oxidase.
In response to certain cytokines and inflammatory mediators, the activity of the neutrophil NADPH oxidase enzyme is primed for enhanced superoxide production when the cells receive a subsequent oxidase-activating stimulus. The relative role of p38 MAPK in the priming and activation processes is incompletely understood. We have developed a 2-step assay that allows the relative contributions of p38 MAPK activity in priming to be distinguished from those involved in oxidase activation. Using this assay, together with in vitro kinase assays and immunochemical studies, we report that p38 MAPK plays a critical role in TNFalpha priming of the human and porcine NADPH oxidase for superoxide production in response to complement-opsonized zymosan (OpZ), but little, if any, role in neutrophil priming by platelet-activating factor (PAF) for OpZ-dependent responses. The OpZ-mediated activation process per se is independent of p38 MAPK activity, in contrast to oxidase activation by fMLP, where 70% of the response is eliminated by p38 MAPK inhibitors regardless of the priming agent. We further report that incubation of neutrophils with TNFalpha results in the p38 MAPK-dependent phosphorylation of a subpopulation of p47(phox) and p67(phox) molecules, whereas PAF priming results in phosphorylation only of p67(phox). Despite these phosphorylations, TNFalpha priming does not result in significant association of either of these oxidase subunits with neutrophil membranes, demonstrating that the molecular basis for priming does not appear to involve preassembly of the NADPH oxidase holoenzyme/cytochrome complex prior to oxidase activation.
Brown
Glenn E
GE
Department of Surgery, Beth Israel Deaconess Medical Center, Boston, Massachusetts 02130, USA.
Stewart
Mary Q
MQ
Bissonnette
Sarah A
SA
Elia
Andrew E H
AE
Wilker
Erik
E
Yaffe
Michael B
MB
D000818:Animals; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D008024:Ligands; D008163:Luminescent Measurements; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000037:antagonists & inhibitors / Q000494:pharmacology; D019255:NADPH Oxidases / Q000378:metabolism*; D018375:Neutrophil Activation / Q000187:drug effects; D009504:Neutrophils / Q000201:enzymology*; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D010972:Platelet Activating Factor / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000037:antagonists & inhibitors / Q000378:metabolism; D013552:Swine; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors / Q000494:pharmacology; D015054:Zymosan / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases
D004791:Enzyme Inhibitors; D007093:Imidazoles; D008024:Ligands; D010750:Phosphoproteins; D010972:Platelet Activating Factor; D011725:Pyridines; D017382:Reactive Oxygen Species; D014409:Tumor Necrosis Factor-alpha; C079789:neutrophil cytosol factor 67K; D009240:N-Formylmethionine Leucyl-Phenylalanine; D015054:Zymosan; D019255:NADPH Oxidases; C060505:neutrophil cytosolic factor 1; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C093642:SB 203580