title: Rac and protein kinase C-delta regulate ERKs and cytosolic phospholipase A2 in FcepsilonRI signaling to cysteinyl leukotriene synthesis in mast cells.
abstract: Although cysteinyl leukotrienes (cysLTs) are known to be principal inflammatory lipid mediators released from IgE-stimulated mast cells, the signaling mechanisms involved in the synthesis of cysLTs remain largely unknown. In the present study, therefore, we investigated the signaling pathway by which IgE induces cysLTs synthesis after binding to its high affinity receptor (FcepsilonRI) in RBL-2H3 mast cells. We found that IgE-induced cysLT synthesis is completely abolished in RBL-2H3(Rac-N17) cells, a stable cell line expressing Rac(N17), a dominant negative Rac1 mutant; conversely, synthesis was enhanced in cells expressing Rac(V12), a constitutively active Rac1 mutant, suggesting that Rac1 is a key mediator of IgE signaling to cysLT synthesis. Further analysis aimed at identifying mediators downstream of Rac1 revealed that pretreating cells with a protein kinase C-delta (PKC-delta) inhibitor or infection with an adenoviral vector harboring a dominant negative PKC-delta mutant significantly attenuates IgE-induced ERKs phosphorylation, cytosolic phospholipase A(2) phosphorylation/translocation, and cysLT synthesis. In addition, the expression of Rac(N17) blocked PKC-delta translocation and impaired the phosphorylation of ERKs and cytosolic phospholipase A(2) otherwise elicited by IgE stimulation. Taken together these results suggest that PKC-delta also plays a critical mediatory role in the IgE signaling pathway leading to cysLT synthesis, acting downstream of Rac1. Finally, the physiological significance of PKC-delta in the IgE signaling pathway was demonstrated in an Ag (OVA)-challenged in vivo mouse model, in which induced levels of cysLTs and airway responsiveness in lung airways were significantly diminished by prior i.p. injection of a PKC-delta inhibitor.
authors.affiliation: School of Life Sciences and Biotechnology, Korea University, 5-1 Anam-dong, Sungbuk-gu, Seoul 136-701, Korea.
authors.forename: Sung-Hoon
authors.initials: SH
authors.lastname: Cho
authors.forename: Hye-Jin
authors.initials: HJ
authors.lastname: You
authors.forename: Chang-Hoon
authors.initials: CH
authors.lastname: Woo
authors.forename: Yung-Joon
authors.initials: YJ
authors.lastname: Yoo
authors.forename: Jae-Hong
authors.initials: JH
authors.lastname: Kim
mesh_terms: D000818:Animals; D001249:Asthma / Q000378:metabolism; D002478:Cells, Cultured; D003545:Cysteine / Q000096:biosynthesis*; D003600:Cytosol / Q000201:enzymology*; D005260:Female; D007073:Immunoglobulin E / Q000502:physiology; D015289:Leukotrienes / Q000096:biosynthesis*; D008407:Mast Cells / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D010741:Phospholipases A / Q000378:metabolism*; D054467:Phospholipases A2; D010766:Phosphorylation; D011493:Protein Kinase C / Q000502:physiology*; D051745:Protein Kinase C-delta; D051381:Rats; D017455:Receptors, IgE / Q000502:physiology*; D015398:Signal Transduction; D020830:rac1 GTP-Binding Protein / Q000502:physiology*
chemical_list: D015289:Leukotrienes; D017455:Receptors, IgE; C112381:cysteinyl-leukotriene; D007073:Immunoglobulin E; D019869:Phosphatidylinositol 3-Kinases; C497259:Prkcd protein, mouse; C497260:Prkcd protein, rat; D011493:Protein Kinase C; D051745:Protein Kinase C-delta; D020928:Mitogen-Activated Protein Kinases; D010741:Phospholipases A; D054467:Phospholipases A2; D020830:rac1 GTP-Binding Protein; D003545:Cysteine