Our group is interested in the maintenance and biological function of epithelial cell polarity. Transporting epithelia form permeability barriers between two compartments of the body (e.g., chyme/ interstitium or interstitum/blood in the gastrointestinal tract) and vectorially transport ions and solutes between these compartments. The highly regulated tight junction constitutes the principal barrier to passive movement of fluid or molecules like glucose and amino acids through the paracellular pathway. In this context we study regulatory molecules including KATP-channels, which are strictly localized to the tight junction area and appear to be involved in the regulation of paracellular permeability.
In an other model of a highly polarized epithelial cell, the gastric parietal cell, we study the regulation of ion secretion through the luminal cell surface. In formation of hydrochloric acid the H+, K+ ATPase is responsible for H+-secretion in the apical membrane. Chloride ions passively follow. We identified anion exchanger2 at the basolateral plasma membrane of parietal cells, being responsible for the chloride uptake. In resting cells the H+, K+-ATPase molecules are stored in the membrane of intracellular tubular vesicles. We are studying the fusion mechanism of these vesicles with the apical plasma membrane and we could show that this fusion process, which is upregulated after stimulation, is mediated by SNARE-proteins.