The research proposed here will address the function and aspects of the regulation of the beta-galactoside binding galectin-4 in adherens junctions of human intestinal epithelial cells. Adherens junctions are involved in cell-cell adhesion and signaling. The maintenance of intestinal epithelial integrity is required for protection against foreign substances as well as the ability to absorb nutrients and transport them to interior tissues. Conditions in which epithelial integrity may be compromised include inflammatory bowel disease, and the metastasis of cancer to secondary sites.
The specific aims of the research proposed here are l) to address the possible role of galectin-4 in vivo by expressing it in a cell line which does not normally express it, and 2) to study the regulation of galectin-4 expression by cytokines and other growth regulators. The human galectin-4 cDNA will be cloned and transfected into the human colonic adenocarcinoma cell line Caco-2 which does not express galectin-4. Development of transepithelial resistance will be used to evaluate the integrity of cellular junctions of control, mock- and galectin-4 transfected cells. Intracellular and extracellular localization of galectin-4 in transfected Caco-2 cells will also be studied by immunocytochemistry and confocal microscopy and compared with known adherens junctions proteins. The effects of cytokines on the expression, secretion and tyrosine-phosphorylation of galectin-4 will be analyzed in T84 cells. Compounds found to regulate these parameters of galectin-4 will also be tested in galectin-4 stable transfectants of Caco-2 cells.
