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This Article Full Text Full Text (PDF) All Versions of this Article: 297/6/C1576    most recent ajpcell.00184.2009v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Yoo, J. Articles by Rozengurt, E. PubMed PubMed Citation Articles by Yoo, J. Articles by Rozengurt, E.

Receptors and Signal Transduction

Protein kinase D mediates synergistic expression of COX-2 induced by TNF- and bradykinin in human colonic myofibroblasts

Departments of Surgery and Medicine, David Geffen School of Medicine, CURE: Digestive Diseases Research Center, and Molecular Biology Institute, University of California, Los Angeles, California

Submitted 29 April 2009 ; accepted in final form 28 September 2009

Myofibroblasts have recently been identified as major mediators of tumor necrosis factor- (TNF-)-associated colitis, but the precise mechanism(s) involved remains incompletely understood. In particular, the possibility that TNF- signaling cross talks with other proinflammatory mediators, including bradykinin (BK), has not been examined in these cells. Here we show that treatment of 18Co cells, a model of human colonic myofibroblasts, with BK and TNF- induced striking synergistic COX-2 protein expression that was paralleled by increases in the levels of transcripts encoding COX-2 and microsomal prostaglandin E synthase 1 (mPGES-1) and by the production of PGE₂. COX-2 expression in 18Co cells treated with BK and TNF- was prevented by the B₂ BK receptor antagonist HOE-140, the preferential protein kinase C (PKC) inhibitors Ro31-8220 and GF-109203X, and Gö-6976, an inhibitor of conventional PKCs and protein kinase D (PKD). In a parallel fashion, TNF-, while having no detectable effect on the activation of PKD when added alone, augmented PKD activation induced by BK, as measured by PKD phosphorylation at its activation loop (Ser⁷⁴⁴) and autophosphorylation site (Ser⁹¹⁶). BK-induced PKD activation was also inhibited by HOE-140, Ro31-8220, and Gö-6976. Transfection of 18Co cells with small interfering RNA targeting PKD completely inhibited the synergistic increase in COX-2 protein in response to BK and TNF-, demonstrating, for the first time, a critical role of PKD in the pathways leading to synergistic expression of COX-2. Our results imply that cross talk between TNF- and BK amplifies a PKD phosphorylation cascade that mediates synergistic COX-2 expression in colonic myofibroblasts. It is plausible that PKD increases COX-2 expression in colonic myofibroblasts to promote an inflammatory microenvironment that supports tumor growth.

18Co cells; prostaglandin E₂; protein kinase C; phosphorylation