PI3K-mediated epithelial sodium channel activity by regulating the apical membrane morphology of renal epithelial cells

Abstract

Continuous high spatial resolution observations of living cells would greatly aid the elucidation of the relationship between structure and function and facilitate the study of major physiological processes such as the mechanism of action of aldosterone on the activity regulation of epithelial sodium channel (ENaC). Unfortunately, observing the micro-structural and functional changes in the membrane of living cells is still a big challenge in current nanomedicine. Scanning ion conductance microscopy (SICM) is such a kind of scanning probe microscopy, which is designed for continuous highresolution topographic imaging of living cells. Under the help of SICM, we have found that aldosterone stimulates ATP release and the basolateral P2X4-like receptors may be involved in the regulation of the activity of ENaC. However, the signaling components linking receptor binding to final ENaC channel regulation remain incompletely characterized. We have now further investigated using SICM and Xenopus A6 kidney epithelial cells that the involvement of the PI3K pathway during the aldosterone action. Three hours continuous SICM observations showed how A6 cells changed their morphology in response to the aldosterone treatment. Patch clamping of individual cells enabled anatomy and function to be correlated, showed that the morphology changed cells with the ENaC channel activity. These morphology changes and ENaC activities were abolished by the specify Phosphoinositide 3-kinases (PI3K) inhibitor LY294002. SICM has the potential to become a powerful tool for research on living renal cells, and has been used to elucidate how PI3K pathway involved in the aldosterone action on renal epithelial sodium reabsorption. © 2008 Springer-Verlag.