Clinical and Functional Study of a De Novo Variant in the PVP Motif of Kv1.1 Channel Associated with Epilepsy, Developmental Delay and Ataxia

Figures

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  Figure 1. EEG during NREM sleep showing frequent and independent epileptiform abnormalities over bilateral frontotemporal regions.

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  Figure 2. (A) Position of identified mutations in the Kv1.1 channel S5–S6 regions, including the P403A variant. (B) Amino acid alignment of Kv1 channels.

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  Figure 3. (A–C) Representative current traces evoked by 200 ms depolarizing steps from a holding potential of −80 to +60 mV from Kv1.1 WT (A), P403A (B), and Kv1.1 WT+P403A (C) channels expressed in HEK 293 cells. The voltage protocol is indicated in the upper panel in (A). (D) Current–voltage relationship for Kv1.1 WT (5 μg), P403A (5 μg) and Kv1.1 WT+P403A (5 μg + 5 μg) channels (n = 14–36). (E) Voltage-dependent activation curves for Kv1.1 WT, P403A, and Kv1.1 WT+P403A channels were obtained by plotting the normalized peak tail currents measured at −50 or −30 mV as a function of the prepulse potentials and fitting data points with a Boltzmann function (n = 10–18 cells).

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  Figure 4. Kinetics of activation (A) and deactivation (B) measured for Kv1.1 WT, P403A and Kv1.1 WT+P403A channels. The time constants, resulting from the fit of the activating and deactivating current traces with a single exponential function, were plotted as a function of voltage (n = 10–19 cells). (C) Bar graphs showing the time constants of the C-type inactivation for the indicated channels calculated by fitting current decay with a single exponential function (n = 9–11 cells). (D) Recovery from inactivation for the indicated channels.

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  Figure 5. (A) Side view of the homology model of the Kv1.1 channel built upon the crystal structure of Kv1.2/2.1 chimera showing the localization of the P403 residue and P403A mutation. P403A is highlighted in magenta. (B) Loss of symmetry of wildtype and P403A measured at the top of S6 (position G385). (C) Measure of the S6 kink angle (left) and symmetry angle (right) for the four subunits of WT and P403A channels. The kink angle of the S6 was measured as the angle between the helix axis of the S6 above and below the PVP/A-motif. The symmetry angles are formed by the vectors from G385 of one subunit to the G385 of the two neighboring subunits. Values are given as mean ± SD of the values measured every 0.1 ns over the last 50 ns.