We investigated proteinase-activated receptor-2 (PAR 2 )-triggered signal transduction pathways causing increased prostaglandin E 2 (PGE 2 ) formation in human lung-derived A549 epithelial cells. The PAR 2 agonist, SLIGRL-NH 2 (Ser-Leu-Ile-Gly-Arg-Leu-amide), evoked immediate cytosolic Ca 2ϩ mobilization and delayed (0.5-3 h) PGE 2 formation. The PAR 2 -triggered PGE 2 formation was attenuated by inhibition of the following signal pathway enzymes: cyclooxygenases 1 and 2 (COX-1 and COX-2, respectively), cytosolic Ca 2ϩ -dependent phospholipase A 2 (cPLA 2 ), the mitogenactivated protein kinases (MAPKs), mitogen-activated protein kinase/extracellular signal-regulated kinase kinase (MEK)-extracellular signal-regulated kinase (ERK) and p38 MAPK, Src family tyrosine kinase, epidermal growth factor (EGF) receptor tyrosine kinase (EGFRK), and protein kinase C (PKC), but not by inhibition of matrix metalloproteinases. SLIGRL-NH 2 caused prompt (5 min) and transient ERK phosphorylation, blocked in part by inhibitors of PKC and tyrosine kinases but not by an EGFRK inhibitor. SLIGRL-NH 2 also evoked a relatively delayed (15 min) and persistent (30 min) phosphorylation of p38 MAPK, blocked by inhibitors of Src and EGFRK but not by inhibitors of COX-1 or COX-2. SLIGRL-NH 2 elicited a Src inhibitor-blocked prompt (5 min) and transient phosphorylation of the EGFRK. SLIGRL-NH 2 up-regulated COX-2 protein and/or mRNA levels that were blocked by inhibition of p38 MAPK, EGFRK, Src, and COX-2 but not MEK-ERK. SLIGRL-NH 2 also caused COX-1-dependent up-regulation of microsomal PGE synthase-1 (mPGES-1). We conclude that PAR 2 -triggered PGE 2 formation in A549 cells involves a coordinated up-regulation of COX-2 and mPGES-1 involving cPLA 2 , increased cytosolic Ca 2ϩ , PKC, Src, MEK-ERK, p38 MAPK, Src-mediated EGF receptor trans-activation, and also metabolic products of both COX-1 and COX-2.Proteinase-activated receptors (PARs), a family of G protein-coupled seven-trans-membrane domain receptors, consisting of PARs 1 to 4, are now known to mediate a variety of intracellular signaling and subsequent cellular events caused by specific extracellular proteinases (Hollenberg

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We investigated possible involvement of three isozymes of prostaglandin E synthase (PGES), microsomal PGES-1 (mPGES-1), mPGES-2 and cytosolic PGES (cPGES) in COX-2-dependent prostaglandin E(2) (PGE(2)) formation following proteinase-activated receptor-2 (PAR2) stimulation in human lung epithelial cells. PAR2 stimulation up-regulated mPGES-1 as well as COX-2, but not mPGES-2 or cPGES, leading to PGE(2) formation. The PAR2-triggered up-regulation of mPGES-1 was suppressed by inhibitors of COX-1, cytosolic phospholipase A(2) (cPLA(2)) and MEK, but not COX-2. Finally, a selective inhibitor of mPGES-1 strongly suppressed the PAR2-evoked PGE(2) formation. PAR2 thus appears to trigger specific up-regulation of mPGES-1 that is dependent on prostanoids formed via the MEK/ERK/cPLA(2)/COX-1 pathway, being critical for PGE(2) formation.

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