Table 1.

Effects of hypoxia, SUMO1 and SENP1 on native I_Na and cloned Na_V1.2 channels. Neurons (Figures 1 and 3) or cloned channels in CHO cells (Figure 5) were studied in whole-cell mode. Stimulation protocols are described in the Materials and methods. V_½, the voltage evoking half-maximal conductance; k, the slope of the curve were obtained by fitting the normalized current plotted against voltage to a Boltzmann function, I = I_max/(1+exp[−(V−V_½)/k]), where I_max is maximum current; and SSI is the steady-state inactivation half voltage. For comparison between groups, current densities were measured both at −20 mV, to demonstrate the impact of the shifts in V_½, and at 0 mV, a potential where the G-V relationships are saturated under all study conditions. The maximal current in CGN cultured at 21% O₂ and studied in ambient O₂ was at −5 ± 1 mV (and the current-density was 292 ± 15 pA/pF); when these neurons were studied with SUMO1 in the pipette or subjected to 5% O₂, the maximal current was observed at −20 ± 2 mV and −20 ± 3 mV, respectively, shifts of ~15 mV analogous to those seen in V_½. When the cells were studied with SENP1 in the pipette, the maximal current was measured at +5 ± 2 mV, a shift of ~10 mV, and the current-density was −288 ± 17 pA/pF. Data are means ± S.E.M. for 10 to 15 cells per group; * indicates p<0.05 compared with cells studied at ambient O₂ under control conditions.

DOI: http://dx.doi.org/10.7554/eLife.20054.005

	INa						NaV1.2						NaV1.2-Lys38Gln
	Activation		SSI		I-20 mV	I0 mV	Activation		SSI		I-20 mV	I0 mV	Activation		SSI		I-20 mV
	V½ mV	k	V½ mV	k	pA/pF	pA/pF	V½ mV	k	V½ mV	k	pA/pF	pA/pF	V½ mV	k	V½	k	pA/pF
Cultured at 21% O2	−23 ± 0.5	4.0 ±  0.2	−67 ± 2	6 ±  1	−172 ± 20	−293 ± 12	−18.7 ± 0.2	3.7 ±  0.1	−59 ± 0.4	7 ± 2	−112 ± 8	−194 ±  10	−4.0 ± 1.5	3.6 ±  0.3	−50 ± 1	6.5 ±  1	−33 ± 7
Lowering O2 21% to 5%	−34 ± 1.5*	4.2 ±  0.2	−78 ± 2*	10 ±  2	−294 ± 25*	−287 ± 18	−30 ± 0.5*	4 ± 1	−72 ± 1.5*	7.5 ±  1	−192 ± 11*	−187 ± 9	−4.0 ± 2	3 ±  1	−49 ± 1	6 ±  1	−35 ± 6*
SENP1	−7.5 ± 1*	4.1 ±  0.3	−53 ± 1*	8 ±  2	−42 ± 12*	−285 ± 17	−2.5 ± 0.3*	3.6 ±  0.1	−48 ± 0.5*	6 ± 1	−29 ± 9*	−191 ±  11	−3.5 ± 1	3.2 ±  0.4	−49 ± 0.5	6.5 ±  2	−35 ± 7*
SUMO1	−36 ± 1*	3.9 ±  0.2	−77 ± 3*	8.5 ±  1	−303 ± 17*	−289 ± 15	−30 ± 0.3*	3.5 ±  0.2	−69 ± 0.5*	7.5 ±  2	−196 ± 17*	−193 ±  12	−4.0 ± 2	3.4 ±  0.5	−50 ± 1.5	6 ±  2	−33 ± 5*
Cultured at 7% O2	−42.9 ± 1.5	3.5 ±  0.5	−57 ±  3	7 ±  2	−162 ±  12			N.D.
Lowering O2 7% to 1.5%	−49.5 ± 1.0	3.2 ±  0.8	−69 ±  2	7 ±  2	−267 ±  18			N.D.