Prostaglandin E₂ Inhibits Proteinase-Activated Receptor 2-Signal Transduction through Regulation of Receptor Internalization

Abstract

ABSTRACT. Proteinase-activated receptor (PAR) is expressed on various cells, and the PAR family consists of PAR1, PAR2, PAR3, and PAR4. Individual PARs are activated during inflammatory conditions in which they regulate inflammatory responses in various diseases. For example, PAR activation is known to induce prostaglandin E 2 (PGE 2 ) production, and then upregulated PGE 2 suppresses PAR1 expression in a negative feedback loop. Surprisingly, PGE 2 effects on PAR2, which is a well-researched and attractive target for drug development, remain unknown. Therefore, we investigated PAR2 regulation by PGE 2 . Using HEK293T cells, we showed that PGE 2 inhibits extracellular signal-regulated kinase (ERK) phosphorylation induced by a PAR2-activating peptide (PAR2-AP). AH-6809 (an inhibitor of PGE 2 receptors 1 [EP1] and 2 [EP2]), but not ONO-AE3-208 (a PGE 2 receptor 4 [EP4] inhibitor), reversed the inhibitory effects of PGE 2 on PAR2-AP-induced ERK phosphorylation. Studies on PAR2 expression revealed that PGE 2 suppressed cell surface expression of PAR2 and induced internalization of PAR2, and not PAR4, in N2a mouse neuroblastoma cells that were transiently transfected with either PAR2 or PAR4. Furthermore, forskolin, an adenylate cyclase activator, induced PAR2 internalization and inhibited PAR2-AP-induced phosphorylation of ERK. Because EP2 (not EP1) also increases intracellular cyclic AMP, we conclude that PGE 2 inhibited PAR2-dependent signal transduction by inducing the internalization of PAR2 through an EP2-dependent increase in intracellular cyclic AMP. This novel regulatory pathway in which PAR2 function is regulated by PGE 2 will broaden our understanding of PAR2-dependent inflammation and could provide novel strategies for drug development. KEY WORDS: cyclic AMP, receptor internalization, prostaglandin E 2 (PGE 2 ), proteinase-activated receptor 2 (PAR2).

Regulation of Epithelial Cell Tight Junctions by Protease-Activated Receptor 2

“…Generation of MDCK cells stably expressing PAR2-mCherry : The lentivirus plasmid used for expressing PAR2-mCherry has been described elsewhere [ 9 ]. To produce the lentivirus plasmids, 3 µ g of pLVmCC human PAR2 plasmid, 2.3 µ g of a packaging plasmid (psPAX2) and 1.3 µ g of a coat-protein plasmid-harboring vesicular stomatitis virus G protein (pMD2.G) were transfected into Lenti-X 293T cells cultured in 60-mm dishes.…”

Proteinase-activated receptors (PARs) – focus on receptor-receptor-interactions and their physiological and pathophysiological impact

“…The PAR 2 interplay with PGE2/EP-signalling in the airway system, defined as a PAR 2 -prostaglandin E2-prostanoid EP receptor axis [78], involves a signalling network triggering arachidonic acid release by the p42/p44 MAPK/cytosolic phospholipase A2 (cPLA2)-pathway downstream from PKC and non-Src tyrosine kinases, upregulation of COX-2 via Src/EGFR/p38 MAPK, and cyclooxygenase-2 (COX-2)-independent NF-κB signalling [69,79-81]. Using HEK 293 T cells, Komatsu et al provided a novel mechanistic aspect for a PAR 2 -PGE2/xEP2 interplay which points to a PGE2-initiated inhibition of PAR 2 -dependent signal transduction by inducing PAR 2 internalization through a prostanoid receptor subtype EP2-mediated increase in intracellular cyclic AMP [82]. Interestingly, for PAR 1 which is also known to be able to induce PGE2 secretion from human respiratory epithelial cells [83] and peritoneal macrophages [84], a very similar mechanism has been described in lung fibroblasts [85].…”

Propionibacterium acnes: an update on its role in the pathogenesis of acne

“…This effect regulates encoding of several proinflammatory cytokines genes (IL-1a, IL-8 and TNF-a), hBD2, as well as of MMPs (1, -2, -3 -9 and -13). PAR-2 is downregulated by the Prostaglandin E2 inducing an internalization of PAR-2 through an EP2-dependent increase in intracellular cyclic AMP E. 31 The activation of the PAR-2 selective antagonist, ENMD-1068 was required for P. acnes to induce the expression of these genes. Overexpression of PAR-2 combined with an increase in global protease activity was observed in vivo in acne lesions.…”