Functional Expression of Rat Nav1.6 Voltage-Gated Sodium Channels in HEK293 Cells: Modulation by the Auxiliary β1 Subunit

The Na(v)1.6 voltage-gated sodium channel alpha subunit isoform is abundantly expressed in the adult rat brain. To assess the functional modulation of Na(v)1.6 channels by the auxiliary beta 1 subunit we expressed the rat Na(v)1.6 sodium channel alpha subunit by stable transformation in HEK293 cells either alone or in combination with the rat beta 1 subunit and assessed the properties of the reconstituted channels by recording sodium currents using the whole-cell patch clamp technique. Coexpression with the beta 1 subunit accelerated the inactivation of sodium currents and shifted the voltage dependence of channel activation and steady-state fast inactivation by approximately 5-7 mV in the direction of depolarization. By contrast the beta 1 subunit had no effect on the stability of sodium currents following repeated depolarizations at high frequencies. Our results define modulatory effects of the beta 1 subunit on the properties of rat Na(v)1.6-mediated sodium currents reconstituted in HEK293 cells that differ from effects measured previously in the Xenopus oocyte expression system. We also identify differences in the kinetic and gating properties of the rat Na(v)1.6 channel expressed in the absence of the beta 1 subunit compared to the properties of the orthologous mouse and human channels expressed in this system.