The PI proposes to determine and characterize the role of villin and its ligands (phosphatidylinositol 4,5- bisphosphate (PIP2) and actin) in epithelial cell motility. Active cell motility regulates many important intestinal epithelial cell functions, including: ion transport proteins via endocytosis and exocytosis, crucial for absorption of nutrients; intestinal restitution, important to maintain homeostasis in the presence of large osmotic and mechanical stress; the movement of cells along the crypt-villus axis; the invasion and propagation of enteropathogens; immune surveillance and inflammation; as well as neoplastic tumor cell dissemination and metastasis. Villin is an actin nucleating, capping, severing, and bundling protein. Villin binds and regulates two ligands that are known to regulate cell motility, phospholipase C-gamma1 (PLC-gamma1) as well as the substrate of the lipase namely, phosphatidylinositol 4,5-bisphosphate (PIP2). Recent studies with villin knock out mice have demonstrated that villin is necessary to regulate epithelial cell motility. In addition, villin shares sequence homology with other proteins of its family including gelsolin, which have been shown to regulate cell motility in vivo. Our working hypothesis is that villin's ability to regulate phosphoinositide-mediated signal transduction pathways and the actin cytoskeleton is important to epithelial cell physiology and pathophysiology involving changes in cell motility. To accomplish our overall study objectives we will characterize the villin-PIP2 interaction using the following approaches: reconstitution in vitro using recombinant villin proteins; endogenous villin expression in the intestinal epithelial cell line, Caco-2; and over expression of villin and enzymes that regulate intracellular PIP2 levels, in the villin null intestinal cell line, IEC-6 using a tetracycline-regulated system. To determine unequivocally the role of villin in the epithelial cell motility, we will use villin knock out mice. These studies promise the prospect of modifying motility for enhancement of normal physiology and for amelioration of disease. Inhibition of epithelial cell motility can be significant in several diseases, including inflammatory bowel disease, celiac disease, and colon cancer.
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