Gap junctions: Cell-cell channels in animals

Gap junctions provide one of the most common forms of intercellular communication. The structures underlying these communicating cell junctions1 were soon resolved in membrane associated particles forming aggregates of six subunits.2 They are composed of membrane proteins that form a channel that is permeable to ions and small molecules, connecting the cytoplasm of acdjacent cells. Two unrelated protein families are involved in this function; connexins, which are found only in chordates, and pannexins, which are ubiquitous and present in both chordate and invertebrate genomes.3 In this chapter, structural and functional issues of gap junction channels are reviewed. Several types of pathologies associated to channel dysfunction, with an emphasis on deafness, are also examined.