Fig. 3: Closed-state inactivation mediated by W-helix.
From: Molecular insights into the gating mechanisms of voltage-gated calcium channel CaV2.3
a Binding pocket of the W-helix. The W-helix is accommodated in a negatively charged pocket on the intracellular side of CaV2.3. The CaV2.3 α1E subunit is shown in the cartoon, and the negatively charged pocket accommodating W-helix is shown as red surface. b Zoomed-in view of the W-helix, which is stabilized in the intracellular gate at a closed state. The W-helix is shown in cartoon and overlaid with an electrostatic surface. W778 and other residues involved in the hydrophobic or charge interactions are shown in sticks. c Activation curves of the wild-type (WT) CaV2.3 and the mutants. CaV2.3 WT, n = 14; Δw-helix, n = 7; CaV2.3RK/A, n = 7. d Steady-state inactivation curves of CaV2.3 WT and the mutants. CaV2.3 WT, n = 9; Δw-helix, n = 8; CaV2.3RK/A, n = 10. e Inactivation ratio quantified using the current density (I) elicited by each spike of AP trains divided by the maximum current (IPeak) elicited by the first spike. CaV2.3 WT, n = 13; CaV2.3 W/Q, n = 15; Δw-helix, n = 9; CaV2.3RK/A, n = 14. f Recovery rate from the CSI, quantified by the inactivation ratio between the two peak currents (I and I2,048ms) obtained in the two-pulse protocol. HEK 293-T cells were held at –40 mV for 1500 ms and were then stepped to –100 mV for a series of time intervals (4–2,048 ms) before a +10 mV test pulse (35 ms). CaV2.3 WT, n = 6; CaV2.3 W/Q, n = 6; Δw-helix, n = 6; CaV2.3RK/A, n = 7. g Representative current responses to the AP trains. The AP trains used to stimulate the HEK 293-T cells were recorded from a mouse hippocampal CA1 pyramidal neuron after current injection in whole-cell current-clamp mode. See Supplementary Figure 5 for voltage-clamp protocols and Method section for literature reference. CaV2.3 WT, black; CaV2.3 W/Q, orange; CaV2.3RK/A, blue. Data are presented as mean ± SEM. n biological independent cells.
