The Apodaca laboratory studies membrane traffic in the specialized epithelial cells that line the nephrons of the kidney and the inner surface of the bladder. Using Madin-Darby canine kidney cells as a model system, we are exploring how kidney cells internalize cell surface receptors and extracellular fluid from either of their discrete apical and basolateral plasma membrane domains, and then how the internalized molecules are processed by the cell. We are particularly interested in a specialized pathway called transcytosis, which allows for transport of endocytosed macromolecules from one plasma membrane domain of the cell to the other.

In the bladder we are studying the umbrella cell layer that lines the inner surface of the organ and forms a tight barrier that accommodates large changes in pressure as the bladder fills and empties. At the cellular level it is hypothesized that this is accomplished by the reversible insertion and retrieval of small discoidal/fusiform vesicles that underlie the apical surface of the umbrella cells. We are interested in defining how the umbrella cells sense changes in stretch, and then how these changes are translated through secondary messenger cascades into vesicle fusion events along with membrane recovery through endocytosis.