Table 1.

Biophysical properties of Ca_v 1.4 WT and CSNB2 mutations

	WT	GD	LP
V_0.5act (mV)
10 mm Ba²⁺	−12.8 ± 0.5; n = 20	−26.5 ± 1.0^***; n = 16	ND
10 mm Ba²⁺ + BayK	−17.7 ± 0.5; n = 35	−35.4 ± 1.0^***; n = 14	−18.6 ± 0.5; n = 12
10 mm Ca²⁺ + BayK	−10.3 ± 0.5; n = 30	−31.8 ± 1.1^***; n = 8	−15.1 ± 0.8^***; n = 15
Activation threshold (mV)
10 mm Ba²⁺	−24.6 ± 0.4; n = 20	−39.4 ± 1.0^***; n = 16	ND
10 mm Ba²⁺ + BayK	−28.7 ± 0.5; n = 35	−45.9 ± 1.2^***; n = 14	−28.6 ± 0.4; n = 12
10 mm Ca²⁺ + BayK	−24.0 ± 0.5; n = 30	−43.2 ± 1.3^***; n = 8	−27.5 ± 0.7^***; n = 15
k_act
10 mm Ba²⁺	−4.7 ± 0.1; n = 20	−4.7 ± 0.2; n = 16	ND
10 mm Ba²⁺ + BayK	−3.9 ± 0.1; n = 35	−4.2 ± 0.3; n = 14	−3.8 ± 0.2; n = 12
10 mm Ca²⁺ + BayK	−5.0 ± 0.2; n = 30	−4.0 ± 0.2^**; n = 8	−4.3 ± 0.2^*; n = 15
Reversal potential (mV)
10 mm Ba²⁺	50.6 ± 0.5; n = 20	44.7 ± 0.9^***; n = 16	ND
10 mm Ba²⁺ + BayK	46.9 ± 0.4; n = 35	44.4 ± 1.3^*; n = 14	46.4 ± 0.9; n = 12
10 mm Ca²⁺ + BayK	53.6 ± 1.3; n = 30	45.3 ± 1.1^**; n = 8	52.6 ± 1.5; n = 15
I_Ba versus I_ca
G_Ba (mS)	12.7 ± 0.7; n = 35	10.0 ± 1.3; n = 14	11.1 ± 1.2; n = 12
G_Ca (mS)	11.1 ± 0.8; n = 30	11.0 ± 1.4; n = 8	13.0 ± 1.2; n = 15
Percentage change (same oocyte)	35.7 ± 2.8; n = 24	−33.9 ± 8.9^***; n = 6	8.8 ± 5.9^***; n = 7

Ca_v 1.4 α1 WT and mutants GD and LP were coexpressed with β3 and α2δ1 subunits in X. laevis oocytes, and their activation properties were determined using 10 mm Ba²⁺ or Ca²⁺ as charge carrier. V_0.5,act, k_act, the reversal potential, and G (maximal slope conductance) were obtained by fitting the data to the Boltzmann equation, as described in Materials and Methods. The activation threshold was determined as the test potential at which 5% of the maximal current was activated. Data are given as mean ± SE; ND, not determined. Note that the shift in V_0.5,act of GD and LP compared with WT could not be explained by currents with different amplitudes, because the differences persisted when smaller (0.25-0.59 μA) or larger (0.6-1.1 μA) currents were analyzed separately (data not shown). BayK, 10 μm BayK present. Conductance was measured in the presence of 10 μm BayK. Statistical differences for V_0.5,act, k_act, activation thresholds, reversal potentials, and G were calculated by one-way ANOVA, followed by the Bonferroni multiple-comparison test or by Student's t test when appropriate. ^*p < 0.05, ^**p < 0.01, ^***p < 0.001 versus WT.