Ionomycin causes activation of p38 and p42/44 mitogen-activated protein kinases in human neutrophils.
Many receptor-linked agents that prime or activate the NADPH oxidase in polymorphonuclear neutrophils (PMNs) elicit changes in cytosolic Ca2+ concentration and activate mitogen-activated protein (MAP) kinases. To investigate the role of Ca2+ in the activation of p38 and p42/44 MAP kinases, we examined the effects of the Ca2+-selective ionophore ionomycin on priming and activation of the PMN oxidase. Ionomycin caused a rapid rise in cytosolic Ca2+ that was due to both a release of cytosolic Ca2+ stores and Ca2+ influx. Ionomycin also activated (2 microM) and primed (20-200 nM) the PMN oxidase. Dual phosphorylation of p38 MAP kinase and phosphorylation of its substrate activating transcription factor-2 were detected at ionomycin concentrations that prime or activate the PMN oxidase, while dual phosphorylation of p42/44 MAP kinase and phosphorylation of its substrate Elk-1 were elicited at 0.2-2 microM. SB-203580, a p38 MAP kinase antagonist, inhibited ionomycin-induced activation of the oxidase (68 +/- 8%, P < 0.05) and tyrosine phosphorylation of 105- and 72-kDa proteins; conversely, PD-98059, an inhibitor of MAP/extracellular signal-related kinase 1, had no effect. Treatment of PMNs with thapsigargin resulted in priming of the oxidase and activation of p38 MAP kinase. Chelation of cytosolic but not extracellular Ca2+ completely inhibited ionomycin activation of p38 MAP kinase, whereas chelation of extracellular Ca2+ abrogated activation of p42/44 MAP kinase. These results demonstrate the importance of changes in cytosolic Ca2+ for MAP kinase activation in PMNs.
Elzi
D J
DJ
Bonfils Blood Center, Denver, CO 80230, USA.
Bjornsen
A J
AJ
MacKenzie
T
T
Wyman
T H
TH
Silliman
C C
CC
D051698:Activating Transcription Factor 2; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling; D002614:Chelating Agents / Q000494:pharmacology; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D004268:DNA-Binding Proteins; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D015759:Ionomycin / Q000494:pharmacology*; D007476:Ionophores / Q000494:pharmacology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D009504:Neutrophils / Q000187:drug effects / Q000201:enzymology*; D010766:Phosphorylation; D010972:Platelet Activating Factor / Q000494:pharmacology; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019284:Thapsigargin / Q000494:pharmacology; D014157:Transcription Factors / Q000378:metabolism; D050807:ets-Domain Protein Elk-1; D048051:p38 Mitogen-Activated Protein Kinases
C497105:ATF2 protein, human; D051698:Activating Transcription Factor 2; D002614:Chelating Agents; D017362:Cyclic AMP Response Element-Binding Protein; D004268:DNA-Binding Proteins; C494112:ELK1 protein, human; D004791:Enzyme Inhibitors; D007476:Ionophores; D010972:Platelet Activating Factor; D011518:Proto-Oncogene Proteins; D014157:Transcription Factors; D050807:ets-Domain Protein Elk-1; D004533:Egtazic Acid; D015759:Ionomycin; D009240:N-Formylmethionine Leucyl-Phenylalanine; D019284:Thapsigargin; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D002118:Calcium