Protein:protein Interactions in Epithelial Physiology
Sponsored by the APS Epithelial Transport Group

The concept of proteins operating in isolation within a cell is one that has been rapidly being eroded in the past few years.  Indeed, it is becoming increasingly apparent that membrane proteins exist in functional networks, not only for trafficking through the cell, but also for function at their final cellular destination.  Much of the work in elucidating these networks has come from studies in polarized epithelia, where it has been shown that both membrane localization and internalization of transporters and channels are highly dependent on specific protein:protein interactions.  As information concerning these interactions in regulating epithelial physiology accumulates, it becomes more important to provide a forum where ideas and insights gained from different aspects of epithelial membrane physiology can be shared.  The focus of this symposium therefore is to examine four distinct areas where protein:protein interactions are of critical importance in the regulation of epithelial function.  The first speaker is Dr. Michael Caplan, who has performed seminal work concerning the sorting and trafficking of ion ATPase pumps, and has recently shown that CD63 is involved in internalization of the H⁺/K⁺ATPase b subunit.  Dr. Daniela Rotin defined the interaction of Nedd4-2 in the internalization of ENaC, and characterized the role of this protein in maintaining the sodium channel at the cell membrane, and thus its influence on epithelial sodium transport.  Dr. Mark  Donowitz is a pioneer in the field of PDZ domain biology as applied to epithelial tissues, particularly as it applies to the interaction of NHERF1/2 to the Na⁺/H⁺ antiport and cytoskeleton in the gut.  Dr. Neil Bradbury was one of the first to demonstrate that the cytoskeletal protein ezrin is involved in the PKA -dependent regulation of CFTR as a result of PDZ domain interactions.  Thus, the proposed speakers cover a broad spectrum of topics of interest to the epithelial community.  While sessions on several similar topics have been presented at previous meetings, the unique epithelial focus and functional emphasis of this symposium, at a point when the field is becoming increasingly complex, is both timely and required.  Furthermore, this symposium intends to bring together some of the leaders in their respective fields, providing an opportunity for a comprehensive assessment of the role of protein:protein interactions in epithelial physiology.