DISTINCT BEHAVIOR OF CONNEXIN56 AND CONNEXIN46 GAP JUNCTIONAL CHANNELS CAN BE PREDICTED FROM THE BEHAVIOR OF THEIR HEMI-GAP-JUNCTIONAL CHANNELS

The gap-junctional protein rat connexin46 (Cx46) has the unusual abili ty to form voltage-gated channels in the nonjunctional plasma membrane of Xenopus oocytes (Paul et al., 1991; Ebihara and Steiner, 1993). Th ese have been suggested to be gap-junctional hemichannels or connexons . The Xenopus oocyte system was used to characterize the functional pr operties of a closely related lens gap-junctional protein, chicken con nexin56 (Cx56) (Rup et al., 1993) and to contrast them to those of rat Cx46. Single oocytes injected with either Cx56 or Cx46 cRNA developed time-dependent, outward currents that activated on depolarization. Th e currents induced by Cx56 and Cx46 showed differences in steady-state voltage dependence and in their degree of rectification. Furthermore, the voltage-dependent properties of the nonjunctional channels induce d by the connexin cRNAs in external solutions containing low concentra tions of calcium ions could account remarkably well for the behavior o f the intercellular channels formed by Cx56 and Cx46 in paired oocytes . These results suggest that many of the voltage-dependent properties of the hemi-gap-junctional channels are retained by the intercellular channels.