Proteinase-activated Receptor-2 Induces Cyclooxygenase-2 Expression through β-Catenin and Cyclic AMP-response Element-binding Protein

Hongying Wang,Shoubin Wen,Nigel W Bunnett,Richard Leduc,Morley D Hollenberg,Wallace K Macnaughton

doi:10.1074/jbc.m703021200

Abstract

Chronic inflammation of mucosae is associated with an increased cancer risk. Tumorigenesis in these tissues is associated with the activity of some proteinases, cyclooxygenase-2 (COX-2), and beta-catenin. Serine proteinases participate in both inflammation and tumorigenesis through the activation of proteinase-activated receptor-2 (PAR(2)), which up-regulates COX-2 by an unknown mechanism. We sought to determine whether beta-catenin participated in PAR(2)-induced COX-2 expression and through what cellular mechanism. In A549 epithelial cells, we showed that PAR(2) activation increased COX-2 expression through the beta-catenin/T cell factor transcription pathway. This effect was dependent upon ERK1/2 MAPK, which inhibited the beta-catenin-regulating protein, glycogen synthase kinase-3beta, and induced the activity of the cAMP-response element-binding protein (CREB). Knockdown of CREB by small interfering RNA revealed that PAR(2)-induced beta-catenin transcriptional activity and COX-2 expression were CREB-dependent. A co-immunoprecipitation assay revealed a physical interaction between CREB and beta-catenin. Thus, PAR(2) up-regulated COX-2 expression via an ERK1/2-mediated activation of the beta-catenin/Tcf-4 and CREB pathways. These findings reveal new cellular mechanisms by which serine proteinases may participate in tumor development and are particularly relevant to cancers associated with chronic mucosal inflammation, where serine proteinases are abundant and COX-2 overexpression is a common feature.

Highlights

Patients with chronic inflammatory diseases of mucosae, including those of the airway and intestine, have an increased risk for the development of cancer
We showed by immunoblotting that the selective PAR2 activating peptide, SLIGRL-NH2, but not the reverse-sequence inactive peptide, LRGILS-NH2, induced a significant increase in COX-2 protein expression (Fig. 1A) 3 h after PAR2 activation
When the concentration of PAR2 by activating peptide (PAR2-AP) was increased to 100 ␮M, a concentration above that which activated ␤-catenin transcriptional activity, we did observe an elevation in ␬B-luciferase activity (Fig. 2E)

Summary

Introduction

Patients with chronic inflammatory diseases of mucosae, including those of the airway and intestine, have an increased risk for the development of cancer. We hypothesized that the ␤-catenin transcription pathway is involved in PAR2-induced COX-2 expression. Using a human epithelial cancer cell line, we show that a selective PAR2 agonist and endogenous activators of PAR2 increase the expression of COX-2 through the activation of the ␤-catenin/Tcf-4 signaling pathway and an ERK-dependent pathway.

Results

Conclusion