Effects of the β1 auxiliary subunit on modification of Rat Na(v)1.6 sodium channels expressed in HEK293 cells by the pyrethroid insecticides tefluthrin and deltamethrin.
We expressed rat Nav1.6 sodium channels with or without the rat β1 subunit in human embryonic kidney (HEK293) cells and evaluated the effects of the pyrethroid insecticides tefluthrin and deltamethrin on whole-cell sodium currents. In assays with the Nav1.6 α subunit alone, both pyrethroids prolonged channel inactivation and deactivation and shifted the voltage dependence of channel activation and steady-state inactivation toward hyperpolarization. Maximal shifts in activation were ~18 mV for tefluthrin and ~24 mV for deltamethrin. These compounds also caused hyperpolarizing shifts of ~10-14 mV in the voltage dependence of steady-state inactivation and increased in the fraction of sodium current that was resistant to inactivation. The effects of pyrethroids on the voltage-dependent gating greatly increased the size of sodium window currents compared to unmodified channels; modified channels exhibited increased probability of spontaneous opening at membrane potentials more negative than the normal threshold for channel activation and incomplete channel inactivation. Coexpression of Nav1.6 with the β1 subunit had no effect on the kinetic behavior of pyrethroid-modified channels but had divergent effects on the voltage-dependent gating of tefluthrin- or deltamethrin-modified channels, increasing the size of tefluthrin-induced window currents but decreasing the size of corresponding deltamethrin-induced currents. Unexpectedly, the β1 subunit did not confer sensitivity to use-dependent channel modification by either tefluthrin or deltamethrin. We conclude from these results that functional reconstitution of channels in vitro requires careful attention to the subunit composition of channel complexes to ensure that channels in vitro are faithful functional and pharmacological models of channels in neurons.
['He|Bingjun|B|', 'Soderlund|David M|DM|']
D000818:Animals D003521:Cyclopropanes D005786:Gene Expression Regulation D057809:HEK293 Cells D006801:Humans D006845:Hydrocarbons, Fluorinated D007306:Insecticides D015640:Ion Channel Gating D008564:Membrane Potentials D062557:NAV1.6 Voltage-Gated Sodium Channel D009570:Nitriles D021122:Protein Subunits D011722:Pyrethrins D051381:Rats
HEK293 cells Pyrethroid insecticide Functional reconstitution Na(v)1.6 isoform Voltage-gated sodium channel β Subunits