Abstract.
Human HeLa cells transfected with mouse connexin Cx30, Cx46 or Cx50 were used to study the electrical properties of gap junction hemichannels. With no extracellular Ca2+, whole-cell recording revealed currents arising from hemichannels. Multichannel currents showed a time-dependent inactivation sensitive to voltage, V m. Plots of the instantaneous conductance, g hc,inst, versus V m were constant; plots of the steady-state conductance, g hc,ss, versus V m were bell-shaped. Single-channel currents showed two conductances, γhc,main and γhc,residual, the latter ≅1/6 of the former. Single-channel currents exhibited fast transitions (1–2 ms) between the main state and residual state. Late during wash-in and early during wash-out of 2 mM heptanol, single-hemichannel currents showed slow transitions between an open state and closed state. The open channel probability, P o, was V m-dependent. It declined from ≅1 at V m=0 mV to 0 at large V m of either polarity. Hemichannel currents showed a voltage-dependent γhc,main, i.e., it increased/decreased with hyperpolarization/depolarization. Extrapolation to V m=0 mV led to a γhc,main of 283, 250 and 352 pS for Cx30, Cx46 and Cx50, respectively. The hemichannels possess two gating mechanisms. Gating with positive voltage reflects V j-gating of gap junction channels, gating with negative voltage reflects a property inherent to hemichannels, i.e., V m or "loop" gating. We conclude that Cx30, Cx46 and Cx50 form voltage-sensitive hemichannels in single cells which are closed under physiological conditions.
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Received after revision and accepted: 11 February 2000
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Valiunas, V., Weingart, R. Electrical properties of gap junction hemichannels identified in transfected HeLa cells. Eur J Physiol 440, 366–379 (2000). https://doi.org/10.1007/s004240000294
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DOI: https://doi.org/10.1007/s004240000294