Fig. 4.

Gap19 inhibits unitary hemichannel currents in HeLa-Cx43 cells. a Whole-cell voltage-clamp recording conditions. b I_m − V_m plot illustrating voltage ramp experiments (−40 to +80 mV, 70 s). Unitary current activity started to appear at +50 mV (control) and was enhanced by further increasing V_m. Experiments with Gap19 or Gap19^I130A in the pipette solution (400 μM) are also shown. c Typical traces of unitary currents activated by stepping V_m from −30 mV to +70 mV for 30 s. Ten consecutive runs (traces) were recorded over 7 min under control conditions (top) and when the pipette solution contained Gap19 (middle) or Gap19^I130A (bottom). d Left: All-point histograms determined from each set of recordings depicted in c. Dashed vertical lines mark peaks in the histograms separated by ~220 pS. Gap19 reduced hemichannel activity as can be appreciated from the decreased number of peaks and increased frequency of the closed state. Right: Open dwell-time histograms determined from the recordings in c. Gap19 decreased the frequency of openings but had no effect on the time constant (τ) of the mono-exponential distribution of open dwell-times. Distributions with Gap19^I130A were as observed in control. Data in c and d are representative for three different experiments. e Bar chart summarizing the results of integrating the current traces over time, giving the membrane charge transfer (Q_m), for the different conditions applied. Gap19 significantly suppressed Q_m to ~1/4 of control while Gap19^I130A had no effect (n = 6 for control, 8 for Gap19 and 6 for Gap19^I130A). f Gap19 inhibited Q_m in a concentration-dependent manner. g Q_m was not influenced by Gap19^I130A unless it was applied at 1 mM concentration