Figure 6.

The peculiarity of rat ASIC1a activation by protons. (a) pH dependence of activation of ASIC1a channels expressed in X. laevis oocytes fitted to the logistic equation F₁ (dotted line) and to equation F₂ (black solid line). Redline reflects pH dependence of activation of model 3–10 corresponding to activation of the channel at the binding of 10 protons with coefficients of cooperativity of p = r = 0.8 and q = s = 0.65, respectively, fitted to equation F₂. (b) pH dependence of activation of the channels expressed in CHO cells fitted to the logistic equation F₁ (dashed line) and to equation F₂ (black solid line). The data were re-plotted from Figure 1k in [38]. Redline reflects pH dependence of activation of model 3–10 corresponding to activation of the channel at the binding of 10 protons with coefficients of cooperativity of p = r = 0.79 and q = s = 0.6, respectively, fitted to equation F₂. (c) Calculated parameters of pH₅₀ for non-discriminated sites, pH₅₀1 for “high-cooperative” sites and pH₅₀2 for “non-cooperative” site are shown as a result of experimental data mathematical processing. (d) pH dependence of ASIC1a activation by protons (black line) and by the combination of protons and 1 mM DAU (red line). ASIC1a held at pH 7.8 was activated by various acidic pH stimuli. I/I_max is the amplitude of the peak current evoked by acidic pH stimuli and normalized to the maximum amplitude (I_max), which we calculated for each cell via individual fitting. Data are presented as mean ± SEM (n = 7); * P < 0.05.