Prostaglandins (PGs) play a fundamental role in the physiology and pathology of the small intestine. PGs modulate various physiological processes including secretion, cytoprotection, epithelial and endothelial barrier function, and motility. Alterations in PG production is also implicated in pathological processes including intestinal carcinogenesis. PGs are produced by intestinal epithelial cells by cyclooxygenases (COX). Acute changes in PG levels in these cells are controlled by COX-2, which is rapidly induced as an immediate-early gene in response to multiple stimuli including inflammatory cytokines and growth factors. Despite the importance of COX-2 in intestinal physiology, little is known about the regulation of COX-2 gene expression in intestinal epithelial cells. Understanding the signaling pathways that regulate the expression of COX-2 in intestinal cells will be important for defining the loss of its control in pathology including intestinal cancer. The broad, long-term objective of this proposal is to elucidate the signal transduction pathways that mediate COX-2 expression in intestinal epithelial cells in response to agonists that act through G-protein coupled receptors (GPCRs). We have identified a new Rho-dependent signaling pathway, activated by agonists of GPCRs, that induces COX-2 expression in fibroblast cell lines. Therefore, we have proposed a model that envisages a novel Rho-dependent signaling cascade that is activated by GPCR agonists in their target intestinal epithelial cells. This proposal will examine the following hypotheses: 1) Agonist occupancy of GPCRs induces COX-2 expression via a Rho-dependent pathway, 2) Signaling by Rho and EGF synergistically induce COX-2 expression in intestinal cells, 3) GPCR activation of Rho is mediated by Galpha12/13 via Rho-specific guanine nucleotide exchange factors (GEFs) or Galphaq via PYK-2 and 4) COX-2 expression is mediated through unique, Rho-specific cis-acting elements on the COX-2 promoter. In order to test these hypotheses, we have formulated four specific aims, which are: 1) Demonstrate and characterize GPCR-mediated COX-2 expression in normal rat intestinal epithelial cells. 2a) Define the role of Ga2/13 signaling in COX-2 expression in intestinal epithelial cells. 2b) Define the role of Gaq and Gai signaling in COX-2 expression in intestinal epithelial cells. 3) Define the role of Rho and of Protein Kinases acting upstream and downstream of Rho in COX-2 expression in intestinal epithelial cells. 4) Characterize COX-2 promoter elements that are responsive to Rho.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK061485-03
Application #
6925543
Study Section
General Medicine A Subcommittee 2 (GMA)
Program Officer
May, Michael K
Project Start
2003-08-21
Project End
2008-07-31
Budget Start
2005-08-01
Budget End
2006-07-31
Support Year
3
Fiscal Year
2005
Total Cost
$309,000
Indirect Cost
Name
University of California Los Angeles
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
092530369
City
Los Angeles
State
CA
Country
United States
Zip Code
90095
Pham, Hung; Vincenti, Romina; Slice, Lee W (2008) COX-2 promoter activation by AT1R-Gq-PAK-p38beta signaling in intestinal epithelial cells. Biochim Biophys Acta 1779:408-13
Pham, Hung; Chong, Benny; Vincenti, Romina et al. (2008) Ang II and EGF synergistically induce COX-2 expression via CREB in intestinal epithelial cells. J Cell Physiol 214:96-109
Pham, Hung; Eibl, Guido; Vincenti, Romina et al. (2008) 15-Hydroxyprostaglandin dehydrogenase suppresses K-RasV12-dependent tumor formation in Nu/Nu mice. Mol Carcinog 47:466-77
Pham, Hung; Shafer, Lindsay M; Slice, Lee W (2006) CREB-dependent cyclooxygenase-2 and microsomal prostaglandin E synthase-1 expression is mediated by protein kinase C and calcium. J Cell Biochem 98:1653-66
Slice, Lee W; Chiu, Terence; Rozengurt, Enrique (2005) Angiotensin II and epidermal growth factor induce cyclooxygenase-2 expression in intestinal epithelial cells through small GTPases using distinct signaling pathways. J Biol Chem 280:1582-93
Shafer, Lindsay M; Slice, Lee W (2005) Anisomycin induces COX-2 mRNA expression through p38(MAPK) and CREB independent of small GTPases in intestinal epithelial cells. Biochim Biophys Acta 1745:393-400