title: Biophysical properties of mouse connexin30 gap junction channels studied in transfected human HeLa cells.
abstract: 1. Human HeLa cells expressing mouse connexin30 (Cx30) were used to study the electrical properties of Cx30 gap junction channels. Experiments were performed on cell pairs with the dual voltage-clamp method. 2. The gap junction conductance (gj) at steady state showed a bell-shaped dependence on junctional voltage (Vj; Boltzmann fit: Vj,0 = 27 mV, gj,min = 0.15, z = 4). The instantaneous gj decreased slightly with increasing Vj. 3. The gap junction currents (Ij) declined with time following a single exponential. The time constants of Ij inactivation (taui) decreased with increasing Vj. 4. Single channels exhibited a main state, a residual state and a closed state. The conductances gammaj,main and gammaj,residual were 179 and 48 pS, respectively (pipette solution, potassium aspartate; temperature, 36-37 degrees C; extrapolated to Vj = 0 mV). 5. The conductances gammaj,residual and gammaj,main showed a slight Vj dependence and were sensitive to temperature (Q10 values of 1.28 and 1.16, respectively). 6. Current transitions between open states (i.e. main state, substates, residual state) were fast (< 2 ms), while those between an open state and the closed state were slow (12 ms). 7. The open channel probability (Po) at steady state decreased from 1 to 0 with increasing Vj (Boltzmann fit: Vj,0 = 37 mV; z = 3). 8. Histograms of channel open times implied the presence of a single main state; histograms of channel closed times suggested the existence of two closed states (i.e. residual states). 9. We conclude that Cx30 channels are controlled by two types of gates, a fast one responsible for Vj gating involving transitions between open states (i.e. residual state, main state), and a slow one correlated with chemical gating involving transitions between the closed state and an open state.
authors.affiliation: Department of Physiology, University of Bern, Buhlplatz 5, CH-3012 Bern, Switzerland.
authors.forename: V
authors.initials: V
authors.lastname: Valiunas
authors.forename: D
authors.initials: D
authors.lastname: Manthey
authors.forename: R
authors.initials: R
authors.lastname: Vogel
authors.forename: K
authors.initials: K
authors.lastname: Willecke
authors.forename: R
authors.initials: R
authors.lastname: Weingart
mesh_terms: D000818:Animals; D015152:Blotting, Northern; D000075302:Connexin 30; D017630:Connexins / Q000235:genetics / Q000502:physiology*; D004594:Electrophysiology; D017629:Gap Junctions / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000502:physiology*; D014162:Transfection
chemical_list: D000075302:Connexin 30; D017630:Connexins; C491020:GJB6 protein, human; C100629:Gjb6 protein, mouse; D009419:Nerve Tissue Proteins