Goblet cells are abundant throughout the gastrointestinal tract and appear to secrete products which form a continuous viscoelastic coat on the mucosal surface of the gastrointestinal tract. In the past, large, densely glycosylated mucin glycoproteins have been the only recognized major secretory product of goblet cells. Recently, the trefoil peptides, a family of structurally distinct small peptides specifically expressed in a regionalize fashion at all levels of the gastrointestinal tract, have been identified as a previously unappreciated major product of goblet onto the mucosal surface where they retain biological activity due to intrinsic resistance to intraluminal degradation. Preliminary studies indicate that trefoil factors form critical constituents at the mucosal- lumenal interface contributing to preservation of mucosal integrity, and protecting against a variety of noxious insults in in vitro model systems. However, there is little insight into the molecular basis of their specific expression in a cell-and tissue-specific manner and the dimensions of their functional activity in sustaining epithelial integrity. The main goals of the studies in this proposal are the elucidation of the features of the genes encoding the trefoil factors and characterization of their protein products in order to both define the molecular basis of goblet cell specific gene expression and to delineate the role of these abundant peptides in sustaining mucosal integrity and function. These goals will be pursued through comprehensive study of the rat and human intestinal trefoil factors (RITF and HITF), identified and cloned in this laboratory which are present in high concentrations in goblet cells throughout the small and large intestinal epithelium. Two major specific aims are planned: (I) Identification of genetic elements responsible for the highly specific expression of ITF in intestinal and colonic goblet cells as well as genetic elements contributing to functional modulation of ITF expression. The latter will be facilitated through the combined application of transient transfection and transgenic techniques and the study of ITF expression in established cell lines. (II) The functional characterization of the biological activities of ITF and other trefoil peptides obtained by direct purification and expression cloning through assessment of their effects on injury of rat and human intestinal and colonic cell lines, and mucosal explants in vitro. Collectively, these studies should provide insights into the trefoil family of proteins and a newly recognized dimension of mucosal biology as well as fundamental insights into the molecular basis of intestinal and goblet cell function. These insights promise to yield new perspective on mechanisms of mucosal destruction, repair and function in inflammatory bowel disease and other forms of injury in the gastrointestinal tract.
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