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The electrical behaviour of rat connexin46 gap junction channels expressed in transfected HeLa cells

Sakai, Rieko ; Elfgang, Claudia ; Vogel, Rolf ; Willecke, Klaus ; Weingart, Robert

In: Pflügers Archiv, 2003, vol. 446, no. 6, p. 714-727

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    Titre
    • The electrical behaviour of rat connexin46 gap junction channels expressed in transfected HeLa cells
    Auteur
    • Sakai, Rieko. Department of Physiology, University of Bern, Bühlplatz 5, 3012, Bern, Switzerland
    • Elfgang, Claudia. Institute of Genetics, University of Bonn, 53117, Bonn, Germany
    • Vogel, Rolf. Cardiology, Swiss Cardiovascular Centre Bern, University Hospital, Inselspital, 3008, Bern, Switzerland
    • Willecke, Klaus. Institute of Genetics, University of Bonn, 53117, Bonn, Germany
    • Weingart, Robert. Department of Physiology, University of Bern, Bühlplatz 5, 3012, Bern, Switzerland
    Type de document
    • Postprint
    Identifiant OAI-PMH
    • oai:doc.rero.ch:321523
    Summary
    Pairs of human HeLa cells expressing rat connexin46 were used to study the electrical properties of gap junction channels with the dual voltage-clamp method. The steady-state conductance (g j,ss) had a bell-shaped dependence on transjunctional voltage (V j). The parameters of the Boltzmann fit were: V j,0=42mV, g j,min=0.12, z=2.5 (pipette solution: K+ aspartate−; 27°C). The Boltzmann parameters were sensitive to the ionic composition of the pipette solution (KCl, K+ aspartate−, TEA+ Cl−, TEA+ aspartate−). The Vj-dependent inactivation of the junctional current I j was approximated by single exponentials (exceptions: two exponentials with KCl at V j≥75mV and K+ aspartate− at V j=125mV). The time constant of inactivation (τi) decreased with increasing V j and was sensitive to the pipette solution. The larger the ions, the slower the inactivation. Recovery from inactivation followed a single exponential. The time constant of recovery (τr) increased with increasing V j. Single-channel currents showed a main state, several substates and a residual state. The corresponding conductances γj,main and γj,residual decreased slightly with increasing V j; extrapolation to V j=0mV yielded values of 152 and 28pS, respectively (K+ aspartate−; 37°C). The values of γj,main and γj,residual were dependent on pipette solution. The ratio γj,main/γj,residual increased with increasing ionic size, suggesting that the residual state impairs ion permeation more severely than the main state. The γj,main data suggest that the ionic selectivity of Cx46 channels may be controlled primarily by ionic size. Compared with hemichannel results, docking of connexons may modify the channel structure and thereby affect the ionic selectivity of gap junction channels. The open channel probability at steady state (P o) decreased with increasing V j. The parameters of the Boltzmann fit were: V j,0=41mV, z=2.2 (K+ aspartate−; 27°C)