FIGURE 1.

GMQ changes the pH dependence of ASIC3 gating and impairs inactivation. Currents were measured by whole-cell patch clamp at a holding potential of −60 mV from CHO cells stably expressing ASIC3. A, current traces of ASIC3 in the absence (top) or presence (bottom) of 1 mm GMQ. Traces obtained at pH 4.0–3.5 (right panel) are of a different experiment. B, ASIC3 was activated by switching from a conditioning pH of 7.4 to various acidic test pH values for 5 s once every 40 s. For the activation curve, the normalized current response is plotted as a function of the stimulation pH for control condition (open symbols) or in the presence of 1 mm GMQ in the acidic test solutions (filled symbols) (n = 4–11). For SSIN, a conditioning pH in the range of pH 7.6–6.5 was applied for 60 s, and the fraction of non-inactivated channels was measured by applying pH 6 for 5 s. This protocol was repeated with increasingly acidic conditioning pH values. In the SSIN curve, normalized currents are plotted as a function of the conditioning pH for the control condition (open symbols) and in the presence of 1 mm GMQ in the conditioning solution (filled symbols) (n = 4–5). For fit parameters, see Table 1. C, pH dependence of the sustained ASIC3 current fraction in the absence or presence of 1 mm GMQ. The ratio of sustained/peak current amplitude is plotted (n = 4–8). Error bars represent S.E.