INTERCELLULAR COMMUNICATION VIA GAP JUNCTION CHANNELS

Gap junction channels maintain cell-cell communication and thus are es sential for the functional co-ordination of tissues and organs. These channels are composed of connexins, a membrane protein family with mor e than a dozen members. Properties of gap junction channels are best s tudied with connexin deficient cells which are transfected with a sele cted connexin gene. We investigated connexin transfected HeLa cells wi th electronmicroscopical (immunogold labelling of freeze fractured rep licas) and electrophysiological (patch clamp and dye transfer) techniq ues. Our results revealed functional gap junction channels outside of quasi-crystalline plaques and give further evidence for different regu lations of channel gating for different connexin isoforms by voltage p olarity of the transjunctional voltage and by intracellular proton con centration. Our model of gap junction channels indicates connexins tha t are integrated in the membrane lipids with different tilt angles and a ring of positive and negative charges within the pore wall that mig ht act as a selectivity filter. (C) 1998 Elsevier Science S.A.