All cells are capable of sampling their environment through a process called endocytosis. Endocytosis is involved in diverse aspects of cellular physiology including modulating responses to growth factors, recycling at nerve terminals, catabolism of internalized nutrients, processing of antigens during immune reactions, and maintenance of cell polarity. During endocytosis both cellular membrane as well as extracellular fluid are internalized and then transported to various intracellular compartments. We are interested in delineating these compartments, determining in which compartments different membrane components and fluid are sorted from one another, and analyzing the regulatory mechanisms that control membrane flow into and out of these compartments. Polarized epithelial cells have increased complexity because they are capable of internalizing macromolecules from either of their discrete apical and basolateral plasma membrane domains.

Our laboratory is also interested in bladder umbrella cells. These epithelial cells sit at the interface between urine and the underlying tissue and have an important barrier function. One little understood aspect of this barrier function is how umbrella cells adapt to the cycles of filling and voiding, and what role they play in the bladder's ability to accommodate large changes in urine volume. One of the goals of our research is to examine the hypothesis that the abundant discoidal vesicles that underlie the apical cell surface of umbrella cells fuse with the apical plasma membrane in response to stretch and thereby increase apical surface area. While our ongoing studies will surely provide us with novel insights into umbrella cell function, they are more broadly significant as stretch-regulated events (which includes exocytosis) underlie much of our sensory perception.

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