Extended Data Fig. 3: Acidic pH negatively modulates the kinetic of GluA2 + TARPy2.
a, Peak amplitude (top panel) and steady state (bottom panel) measured from 200 ms of 10mM L-glutamate applications in pH 7.4 (black) and 5.5 (red) from GluA2+TARP y2, n = 27 patches. Boxes, whiskers, and lines as in Fig. 3b. Dotted lines show mean peak currents. Asterisks show comparisons for peak amplitude; two-sided, Wilcoxon matched-pairs signed rank test, P < 0.0001 and for steady-state; two-sided paired t-test: t = 14.98, df = 26, ****P = 0.0001. b, Representative responses evoked by 10 mM glutamate (1 ms, −60mV) in pH 7.4 (black line) and 5.5 (red line) from the outside-out patch (GluA2 + TARPy2). The inset shows scaled-to-peak responses. c, Boxplots showing weighted deactivation time constant (left panel), rise time constant (middle panel), and peak amplitude (right panel) measured from current responses to 1 ms, 10 mM glutamate applications (GluA2 + TARPγ2, n = 11 patches). Boxes, whiskers and lines as in Fig. 3b. Asterisks show comparisons for deactivation time constant: two-sided pair sample t-test: t = 6.167, df = 10, ***P = 0.0001, rise time constant: two-sided pair sample t-test: t = 6.574, df = 10,****P < 0.0001 and peak amplitude: two-sided, Wilcoxon matched-pairs signed rank test, P = 0.001. d, Whole-cell current responses (GluA2 + TARPγ2) to L-glutamate concentrations applied at pH 7.4 (black traces, left panel) and at pH 5.5 (red traces, middle panel). The left panel shows averaged and normalized concentration-response curves to L-glutamate obtained in pH 7.4 (black circles, n = 6 cells) and in 5.5 (red circles, n = 6 cells) error bars are SEM. Current responses were normalized to the response to 10 mM glutamate. e, Current responses from an outside-out patch containing GluA2 + TARPγ2 to 10mM L-glutamate, 200 ms, holding voltage −60mV. Grey traces show responses in pH 7.4 and salmon traces show responses in pH 5.5. The black and red lines show averaged responses in pH 7.4 and 5.5. The inset shows the corresponding current-variance relationship, estimated channel conductance (γ), and open probability at the peak (Po) in pH 7.4 (black) and 5.5 (red). f, Boxplots show the effect of pH 5.5 on the mean channel conductance (γ), and open probability estimates for the GluA2 + TARPγ2, n = 11 patches. Boxes, whiskers, and lines as in Fig. 3b. Indicated P values are from the two-sided pair sample t-test, channel conductance: t = 1.224, df = 10, P = 0.2492 and the peak open probability: t = 4.622, df = 10, P = 0.0009.
