Cell adhesion Gap junctions
Gap junctions Gap junction channels are intercellular channels that allow passage of ions, such asK(+) and Na(+), and other small molecules between neighboring cells. Thesechannels are formed from two multimeric subunits called hemichannels, or connexons, thatreside in plasma membranes of two closely opposed cells. Connexons are composed of six transmembrane protein subunits called Connexins. The double membrane channel, or gap junction, is generated directly andcouples the cytoplasms of the interacting cells. This leads to integration andco-ordination of the cellular metabolism, signaling and function, e.g.,secretion orcontraction in cell assemblies . Interactions of Connexins with Zona occludens proteins ( ZO-1,ZO-2 and ZO-3 ) couple gap junction channels with the tight junctioncomponents, such as Occludin, and with cytoskeletal elements, such asActin filaments . Connexins 43 and 36 can anchor Microtubules (consisting of theAlpha/Beta-tubulin dimers) to gap junctions and thereby can affect the propertiesof microtubules in contacted cells , .