Intercellular communication via gap junction channels

Gap junction channels maintain cell-cell communication and thus are essential for the functional co-ordination of tissues and organs. These channels are composed of connexins, a membrane protein family with more than a dozen members. Properties of gap junction channels are best studied with connexin deficient cells which are transfected with a selected connexin gene. We investigated connexin transfected HeLa cells with electronmicroscopical (immunogold labelling of freeze fractured replicas) and electrophysiological (patch clamp and dye transfer) techniques. Our results revealed functional gap junction channels outside of quasi-crystalline plaques and give further evidence for different regulations of channel gating for different connexin isoforms by voltage polarity of the transjunctional voltage and by intracellular proton concentration. Our model of gap junction channels indicates connexins that are integrated in the membrane lipids with different tilt angles and a ring of positive and negative charges within the pore wall that might act as a selectivity filter. (C) 1998 Elsevier Science S.A.