Platelet-activating factor activates mitogen-activated protein kinases through the activation of phosphatidylinositol 3-kinase and tyrosine kinase in human eosinophils.
We determined whether platelet-activating factor (PAF) activates mitogen-activated protein (MAP) kinases in human eosinophils, and if so, which signaling pathways are utilized for the MAP kinase activation. PAF activated 42-and 44-kDa MAP kinases (ERK1/ERK2) in eosinophils, which became maximal at 1 min after stimulation. The PAF receptor antagonist E6123 and pertussis toxin inhibited the PAF-induced MAP kinase activation in eosinophils. The phosphatidylinositol 3-kinase (PI 3-kinase) inhibitor wortmannin, tyrosine kinase inhibitors herbimycin A and genistein, and an intracellular Ca2+ chelator BAPTA/AM inhibited PAF-induced MAP kinase activation in eosinophils, whereas protein kinase C inhibitors staurosporine and calphostin C had no effect. Furthermore, wortmannin as well as herbimycin A and genistein, but not BAPTA/AM, prevented PAF-induced tyrosine phosphorylation of Shc adapter protein in eosinophils. Finally, the specific MEK inhibitor PD98059 inhibited PAF-induced chemotaxis in eosinophils. Taken together, these results indicate that PAF activates MAP kinases in eosinophils through the activation of PI 3-kinase and a tyrosine kinase and the increase in intracellular Ca2+ and that PAF-induced MAP kinase activation mediates chemotaxis in eosinophils.
Miike
S
S
Department of Internal Medicine II, Chiba University School of Medicine, Chiba City, Japan.
Kurasawa
K
K
Saito
Y
Y
Iwamoto
I
I
D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D004789:Enzyme Activation; D004804:Eosinophils / Q000378:metabolism*; D006801:Humans; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010972:Platelet Activating Factor / Q000378:metabolism* / Q000494:pharmacology; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects
D010972:Platelet Activating Factor; D019869:Phosphatidylinositol 3-Kinases; D011505:Protein-Tyrosine Kinases; D020928:Mitogen-Activated Protein Kinases; D002118:Calcium