Exploring Hemichannel Permeability In Vitro

Abstract

The intercellular molecular signaling that occurs though gap junctions is determined by the particular molecules that can pass through the specific connexin channels involved. Differences in the biological roles played by different connexin isoforms are no doubt due, in part, to differences in the molecular selectivity of the channels they form. The molecular selectivity of connexins can be investigated in cells by monitoring intercellular movement of fluorescent or radiolabeled tracers. The tracers must be either injected into cells or loaded via acetoxymethyl (AM)-ester or similar chemistry. This approach has the advantage of working with native gap junction structures, but the disadvantage of being limited to the use as tracers of molecules that are tolerated well by cells and that do not affect connexin expression or function. In addition, enzymatic activities in cytoplasm can cause serious problems for interpretation of results, particularly for biologically active junction-permeant molecules such as second messengers.