The umbrella cells lining the mucosal surface of the urinary bladder form a barrier between the urine and the underlying muscle layers and vasculature. The barrier function of the uroepithelium depends on several factors including: (i) formation of a polarized epithelium with tight junctions; (ii) presence of an apical membrane highly impermeable to water, urea, and toxic components of urine; and (iii) a surface layer of glycosaminoglycans and mucins that protect the underlying epithelium and may prevent bacterial adhesion to the umbrella cell plasma membrane .

We are examining an additional aspect of umbrella cell barrier function that is currently only poorly understood: the requirement that the epithelium accommodate large variations in bladder volume - a function hypothesized to be mediated in part by discoidal vesicles that are inserted/removed from the apical membrane of the umbrella cell in response to filling and emptying. Our goal is to understand how a mechanical stimulus (stretch) results in changes in vesicle traffic (exocytosis of discoidal vesicles). In addition, we are examining if stretch also regulates endocytosis in these specialized epithelial cells.

Current projects in the laboratory include:

I. Analysis of endocytic pathways in polarized MDCK cells
II. Regulation of endocytic traffic by Rho family GTPases
III. Stretch-regulated endocytosis/exocytosis in bladder uroepithelium