application) The overall aim of this project is to better define the characteristics of intestinal epithelial cell-neutrophil interaction as it relates to fluid and electrolyte secretion. Many intestinal disorders, particularly the acute flare of inflammatory bowel disease (IBD), are characterized by migration of neutrophils across the intestinal epithelium into the lumen to form 'crypt abscess'. Crypt abscesses are pathognomic of active IBD and infectious colitis and correlate with severity of disease as well as clinical symptoms. We have previously shown that neutrophil migration into the intestinal lumen elicits electrogenic chloride secretion (secretory diarrhea) and the major effector of this chloride secretory response is the neutrophil-derived secretagogue, 5'AMP. Intestinal epithelia express an ectonucleotidase, which converts 5' AMP to adenosine which then interacts with intestinal epithelial adenosine 2b (A2b) receptor to elicit chloride secretion. Thus the A2b receptor plays a central role in orchestrating chloride secretion induced by neutrophils. An understanding of the regulation and signaling mechanism of A2b receptor may therefore lead to designing of novel treatments for this component of IBD. In this proposal, I intend to characterize the biology of intestinal A2b receptor using two intestinal epithelial cell models: T84 cells and Caco-2 bbe cells transfected with the A2b receptor. A2b receptor is the only adenosine receptor in T84 cells while Caco-2 bbe cells lack A2b receptor. First, I will study the polarity of surface expression, distribution, kinetics of turnover, structural requirements for ligand binding, desensitization, and G-protein recognition. Second, I will analyze the existence of ectonucleotidase and A2b receptor in signaling membrane microdomain such as caveolae. These microdomains represent invagination of plasma membrane enriched in glycosphingolipid, which have been shown to contain signaling proteins. Third, I will study the role of adenosine receptor in the modulation and feedback regulation of neutrophil-epithelial interaction including transmigration and chemokine secretion.
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