Transcellular secretion of group V phospholipase A2 from epithelium induces beta 2-integrin-mediated adhesion and synthesis of leukotriene C4 in eosinophils.
We examined the mechanism by which secretory group V phospholipase A(2) (gVPLA(2)) secreted from stimulated epithelial cells activates eosinophil adhesion to ICAM-1 surrogate protein and secretion of leukotriene (LT)C(4). Exogenous human group V PLA(2) (hVPLA(2)) caused an increase in surface CD11b expression and focal clustering of this integrin, which corresponded to increased beta(2) integrin-mediated adhesion. Human IIaPLA(2), a close homolog of hVPLA(2), or W31A, an inactive mutant of hVPLA(2), did not affect these responses. Exogenous lysophosphatidylcholine but not arachidonic acid mimicked the beta(2) integrin-mediated adhesion caused by hVPLA(2) activation. Inhibition of hVPLA(2) with MCL-3G1, a mAb against gVPLA(2), or with LY311727, a global secretory phospholipase A(2) (PLA(2)) inhibitor, attenuated the activity of hVPLA(2); trifluoromethylketone, an inhibitor of cytosolic group IVA PLA(2) (gIVA-PLA(2)), had no inhibitory effect on hVPLA(2)-mediated adhesion. Activation of beta(2) integrin-dependent adhesion by hVPLA(2) did not cause ERK1/2 activation and was independent of gIVA-PLA(2) phosphorylation. In other studies, eosinophils cocultured with epithelial cells were stimulated with FMLP/cytochalasin B (FMLP/B) and/or endothelin-1 (ET-1) before LTC(4) assay. FMLP/B alone caused release of LTC(4) from eosinophils, which was augmented by coculture with epithelial cells activated with ET-1. Addition of MCL-3G1 to cocultured cells caused approximately 50% inhibition of LTC(4) secretion elicited by ET-1, which was blocked further by trifluoromethylketone. Our data indicate that hVPLA(2) causes focal clustering of CD11b and beta(2) integrin adhesion by a novel mechanism that is independent of arachidonic acid synthesis and gIVA-PLA(2) activation. We also demonstrate that gVPLA(2), endogenously secreted from activated epithelial cells, promotes secretion of LTC(4) in cocultured eosinophils.
Muñoz
Nilda M
NM
Section of Pulmonary and Critical Care Medicine, Department of Medicine, The University of Chicago, 5841 South Maryland Avenue, Chicago, IL 60637, USA.
Meliton
Angelo Y
AY
Lambertino
Anissa
A
Boetticher
Evan
E
Learoyd
Jonathan
J
Sultan
Faraz
F
Zhu
Xiangdong
X
Cho
Wonhwa
W
Leff
Alan R
AR
D016718:Arachidonic Acid / Q000037:antagonists & inhibitors / Q000502:physiology; D018821:CD18 Antigens / Q000502:physiology*; D002448:Cell Adhesion / Q000276:immunology; D002460:Cell Line; D003600:Cytosol / Q000201:enzymology; D004804:Eosinophils / Q000276:immunology* / Q000378:metabolism*; D004847:Epithelial Cells / Q000201:enzymology* / Q000378:metabolism*; D054505:Group V Phospholipases A2; D006801:Humans; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology; D017997:Leukotriene C4 / Q000096:biosynthesis*; D008244:Lysophosphatidylcholines; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D010741:Phospholipases A / Q000378:metabolism* / Q000502:physiology; D054467:Phospholipases A2; D010766:Phosphorylation; D021381:Protein Transport
D018821:CD18 Antigens; D007527:Isoenzymes; D008244:Lysophosphatidylcholines; C006065:We 201; D016718:Arachidonic Acid; D017997:Leukotriene C4; D009240:N-Formylmethionine Leucyl-Phenylalanine; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D010741:Phospholipases A; D054505:Group V Phospholipases A2; C516299:PLA2G5 protein, human; D054467:Phospholipases A2