Background: Phosphatidylinositol-3-kinase (PI3-kinase) comprises an essential component in a number of signaling cascades, primarily of the growth factor type. Two specific inhibitors, wortmannin and demethoxyviridin (DMV), are widely used to block signaling via this molecule and link certain receptors to the PI3-kinase pathway Methods: We have studied the extent of involvement of PI3-kinase in signaling events by FcεRI in mast cells using a mouse mast cell line as a model system. This was done using β-hexosaminidase release assays, a leukotriene ELISA, transient transfections with reporter gene constructs of TNFα and MARC, and in addition a TNFα ELISA. Results: Consistent with previously published data in the rat basophilic cell line RBL-2H3, we find that wortmannin as well as DMV prevent the degranulation reaction in the mouse mast cell line CPU. DMV also inhibits the release of leukotrienes, leading to the conclusion that FcεRI activates PI3-kinase which then mediates these reactions. On the contrary, however, lymphokine and chemokine induction at the gene and protein level is not inhibited, suggesting that the activation of this gene set in mast cells is independent of PI3-kinase. Conclusion: PI3-kinase is activated in our mast cell model system via cross-linking of the FcεRI. This reaction is clearly necessary for the degranulation process and the release of leukotrienes. Activation of lymphokine and chemokine genes as well as secretion of their gene products are not triggered along the PI3-kinase signaling pathway. This is in agreement with our previous findings, showing that the MAP kinase pathway and Ca2+ influx are both involved in gene activation in this cell type.

Keywords:
Cytokines, Degranulation, Demethoxyviridin, Gene induction, Leukotrienes, Mast cells, Phosphatidylinositol-3-kinase, TNFα, Wortmannin
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© 1997 S. Karger AG, Basel
1997
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